Room for improvement: Self-critique of the Flex Capacitor 40-60 Pack

On the summit of James Peak with the Flex Capacitor, the fifth and final 13'er of the day, looking south towards Bancroft, Parry, Eva, and Flora.

On the summit of James Peak with the Flex Capacitor, the fifth and final 13’er of the day, looking south towards Bancroft, Parry, Eva, and Flora.

Recently I highlighted seven standout specs and features of the Sierra Designs Flex Capacitor 40-60 Pack. Today, I’ll do nearly the opposite: identify its imperfections.

Since I co-developed the Flex Capacitor with Sierra Designs, naturally I want to see strong sales of it. But I also want prospective buyers to understand its optimal applications and tradeoffs, and ultimately find the best backpack for them. All else being equal, I hope you will support my forthrightness.

1. Limited sizing and color options

A limited production run will become available in October, directly from Sierra Designs. Sign up for updates. It will come in one color scheme and three unisex torso-length sizes (S, M, and L).

The color option will not change for retail distribution in spring 2017, but sizing will. It will consolidate to unisex S/M and M/L, which will still have 3-inch ranges but which will cover most of the market with one less SKU.

These limited sizing and color options will limit interest in the Flex Capacitor, especially among women and among men with very short or very tall torsos. But due to SD’s newcomer status and to the state of the retail backpack market (i.e. dominated by Osprey, with a few pegs leftover for everyone else), SD believes that a tight assortment is its best hope of gaining a foothold.

2. It’s not “ultralight.”

With relative ease, we could have substantially reduced the weight of the Flex Capacitor, which currently specs at 2.5 pounds (1.1 kg). How? Mostly, by:

  • Eliminating its full suspension, back panel padding, and hipbelt;
  • Removing its six exterior pockets;
  • Using a lighter weight fabric; and,
  • Shrinking its volume, or at least making it static (rather than adjustable).

These actions may have pleased the thru-hiking community, BPL forums, and r/Ultralight, but it would have left the broader market longing for more. Frankly, I’d be looking elsewhere, too. IMHO, the extra 16-24 ounces is well worth the improved load-carrying performance, convenience, durability, and versatility.

3. No rear shove-it pocket, sleeping bag compartment, or tall side pockets

The single most standout feature of the Flex Capacitor is its adjustable volume, using the gusset on its frontside. Unfortunately, this feature is incompatible with a rear shove-it pocket and a sleeping bag compartment.

Oh, well.

Shove-it pockets compromise load-carrying performance (because the weight is far from the user’s center of gravity, and often sits outside the compression system) and are abrasion-prone if made of mesh. When using the Flex Capacitor, I store oft-needed items in exterior pockets or at the top of the main compartment (easily accessible via the zippered top lid); and I store wet items like my rain gear and tent fly inside the main compartment but outside my pack liner.

I struggle to see the case for sleeping bag compartments, and wonder if they are just a relic from a bygone era when sleeping bags were much less compact. When I pull into camp, everything must come out of my pack — shelter, food bag, stove, puffy layers, etc. Why is a second access point supposedly more convenient?

Finally, tall side pockets are not accessible without taking off the backpack. At that point, why store items outside the pack, when they would carry better and be more secure inside the main compartment?

Rear shove-it pockets are conveniently accessible, but they don't carry weight well and they're abrasion-prone when made of mesh.

Rear shove-it pockets are conveniently accessible, but they don’t carry weight well and they’re abrasion-prone when made of mesh.

4. Lack of “wrap”

Frameless backpacks fit like a glove — they conform to the user’s back, not the other way around. Unfortunately, frameless packs cannot comfortably carry loads of 25-ish pounds or more. To carry more weight, you must use a full suspension backpack.

Whether in a frameless or full suspension pack, weight carries best when it is flush against the back, so that it minimally affects the user’s center of gravity. Unfortunately, this direct contact results in SBS, or “sweaty back syndrome,” especially in hot and humid conditions.

To avoid SBS, there must be airflow between the user and the backpack. Unfortunately, this pushes the load backwards and compromises load-carrying.

See the tradeoffs?

The Flex Capacitor is a full suspension backpack with decent airflow around the kidneys. But it does not “wrap” the user like a frameless pack will, and its load-carrying is not at max potential. Further refinements to the back panel pods and hip belt may improve things.

The Flex Capacitor has a stiff Y-shaped internal stay (pulled out for this photo) and a three-pod back panel that provides airflow around the kidneys.

The Flex Capacitor has a stiff Y-shaped internal stay (pulled out for this photo) and a three-pod back panel that provides airflow around the kidneys.

5. Stretch mesh side pockets

The side pockets on early Flex Capacitor prototypes were made of durable pack body fabric. They were easily accessible and could be locked off when bushwhacking. But their bulbousness ruined the pack’s otherwise “clean” look, and the lock-off was clumsy.

The side pockets are now made of stretch mesh. They look much cleaner, and they are still easily accessible — they have some dimension, and are not flush against the pack body. However, they will be more abrasion-prone, even though we’re using the heaviest mesh available, and there is no security feature.

6. Top lid zipper snags and aesthetics

The Flex Capacitor’s main compartment is accessed through a zippered top lid. Getting in or out is refreshingly quick, relative to the sequence of buckles, straps, cords, and roll-tops on most packs.

However, it’s not entirely annoyance-free, as the #10 zipper can snag on the rainguard. We could have eliminated the rainguard by using a watertight zipper. But such zippers are:

  • Expensive
  • Less durable
  • Less easy-gliding
  • Not waterproof in extended wet conditions

Plus, we didn’t want to give the illusion that the pack is waterproof when it is not. To keep dry items in the main compartment, I recommend using a 20-gallon Brute trash compactor bag.

Unless the pack is stuffed full, the top lid will sag and “mushroom.” It’s merely an aesthetic issue, and common among packs with top lids.

When not stuffed full, the top lid will sag and create a "mushroom" look.

When not stuffed full, the top lid will sag and create a “mushroom” look.

Disclosure: This post contains affiliate links, which help to support this website.

Posted in on August 31, 2016
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  1. MarkL on August 31, 2016 at 11:23 am

    I like it when a company tries to break out of a design rut and offer something new. This echos some other concepts out there, such as the venerable Wild Things Andanista, but with a broader target customer.

    First a couple questions:
    1: Seasonal versatility: Is the pack body material durable enough to use as a 4-season pack, where you may be strapping snow shoes to the front or sides? You also say no metal edged skis. What is the particular issue with them? The straps or the pack body?
    2: Frame: Since it is a tubular frame I assume the stays can’t be re-shaped to conform to the user as you can with removable flat stays. Are there other ways to “customize” the fit for different body types? Or is the idea that its rigidity actually makes it carry closer to a traditional external frame?
    3: Sizing: You mentioned different sizes and belts. Can you mix an match those at purchase, or will you need to buy the pack and then a different belt as an accessory?

    A few other thoughts:
    1: Thank you for putting out a product that doesn’t cave to the ultra-light fanaticism that seems to be dominating the conversation recently. There is a balance between weight, durability, versatility, comfort, price, etc., and for most people weight is not (or shouldn’t be) the defining issue. This at least looks like an honest attempt to find that balance. So far I feel the same way about the Tarptent I recently purchased. I could have gone lighter, but I would either have had gossamer fabrics, had to give up some comfort/livability space and features, or paid 3 times as much. As it is, I have a very livable shelter (decent space for 2, a palace for one) that is still half the weight of my previous 2-person. This looks like it is born of a similar philosophy.
    2: Re Shove-it pocket: I have old (like 15 years old) Madden Mountaineering packs and the pocket is absolutely part of the compression system. Seems like that is not that unusual in the packs I’ve looked at recently, but I’ll have to look more closely. I mostly use it for flat things like my map case and shovel blade. That being said, this doesn’t seem like a winter-oriented pack, so that may be a reasonable design sacrifice.
    3: Re top pocket: I have always liked a hinged or floating lid. In general I don’t like relying on zippers on a pack, especially in a critical area. I like being able to just tuck a coat (or a sleeping pad, or a climbing rope) under it. If I end up having to carry a partners stuff it is easier to overpack. Just in general it seems like a more versatile design.
    4: I agree that the sleeping back compartment is unnecessary, although I now find myself using the one on my old pack for my bag, pad, rain gear, etc. It’s accessibility actually negates some of what I have traditionally used the shove-it and floating lid for.

    • Andrew Skurka on August 31, 2016 at 12:49 pm

      1. I would feel comfortable with strapping snowshoes to the pack, but I’d be wary of metal-edged skis due to the sharp edges, especially if the pack fabric is sandwiched between the ski and something hard like a stove pot.

      2. No, it cannot be user-adjusted. Retailers and SD team members (notably that of one of the main designers, who was formerly at Osprey) were consistent in their opposition to this. Basically, many more people screw it up than get it right.

      3. The hipbelts will be matched with packs of the same torso length, e.g. medium hipbelts on medium sizes. But SD and retailers will have extra hipbelts available so that you get the right fit. It would make sense if you could order a torso and hipbelt size when you purchase the pack at, to avoid playing mail tag, but I can’t confirm that.

      • Fowler on August 31, 2016 at 10:15 pm

        #2 strikes a chord, most won’t come out and say it (kudos) but a lot of designing for the public is constraining their opportunities to mess up a product. This is “lowest common denominator” stuff, but it is the reality of business. Cottage companies can get away with much more, but anyone selling retail has to deal with this front and center.

  2. robin on August 31, 2016 at 1:36 pm

    Aside from the obvious unique feature of the adjustable capacity, this bag really only compares two a couple others on the market that I can think of: the ULA Circut, and the Osprey Exos, and the Gossamer Gear Gorilla/Mariposa. I wonder if you might write up a comparison of these products. (I’m sure there are others, but these are very popular packs in same weight/size that feature full suspension). I had narrowed it down to those few packs before yours came out and went with an Exos 48 that I found at a garage sale. It’s been killer all summer – large enough to hold everything I need for a 9 day high sierra trip, and as lightweight as I would want for pack weights between 18-35 lbs. The mesh pockets are showing wear, but other than that it’s been great. Other than the increased capacity and adjustability, what else does your pack have going for it over the Exos, Circut, or Gorilla/Mariposa? (comfort, durability, load carrying, etc?)

    • Andrew Skurka on August 31, 2016 at 2:11 pm

      I can only comment credibly about the Circuit, which I’ve used personally and which I’ve lent to a lot of guided clients. The other comments are speculation.

      In general, the three packs in question will have more size and color options. The Flex Capacitor will be more versatile due to the adjustable volume — it’s like a Circuit/Catalyst, Exos 48/58, and Mariposa/Gorilla in one.

      Versus the Circuit, the Flex’s suspension carries heavier loads better, because it’s stiffer and anchors directly into the hipbelt; the top of the stay is also higher, so more weight can be be released off the shoulders. Cleaner access to the main compartment (vs roll top). Less expensive by about $50. Similar functionality for the hipbelt and side pockets. The ULA packs ride closer and “wrap” better, but have no airflow through the back panel. They have rear shove-it pockets, if you like that feature. The ULA packs are made in the USA, use more premium fabrics, and the owner Chris will pick up the phone if you call.

      The Osprey probably fits better. Suspension is less capable. Side pockets are less accessible. Main compartment access has more steps.

      The Gorilla is much more limited with load-carrying. Its exterior pockets are convenient, but for my purposes I would rather everything be inside the pack, where it carries best and is more secure.

  3. Robin on August 31, 2016 at 2:59 pm

    What do you mean the Osprey fits better? A more fitting comparison, or actually will fit my body better?

    • Andrew Skurka on August 31, 2016 at 3:06 pm

      In general, the Osprey has a more body-sculpted fit. But that’s not to see it will always fit you better. For example, read about Dale’s recent experience with the Exos.

      Backpacks are only one notch below footwear in the finickiness of their fit. YMMV.

  4. David on August 31, 2016 at 7:08 pm

    Andrew, if you want to see the perfect side water bottle pocket in action, have a look at Mchale Packs. They are removable, you can adjust the height of them on the pack, and you can angle them for really easy access to a water bottle or you can have them verticle to carry things you want to stay put.

  5. Shawn K. on August 31, 2016 at 8:25 pm

    Public self-critique? That’s not how you’re supposed to behave! It’s almost like you care about having your name attached to a project. 🙂

    I recently changed packs and I find a two strap hip belt to be more supportive and comfortable, as the top & bottom can be adjusted separately for a custom fit. Better fitment also may reduce the amount of hip belt padding required, which should help offset the weight & cost of the new design.

    It looks like a good balance was struck between pockets/features and weight. Over time, I’ve grown to dislike sleeping bag compartments and other internal organizational efforts. They just get in the way, while adding weight & cost. The same goes for attempts at waterproofing the pack; watertight zippers aren’t worth the bother.

    I look forward to seeing more Skurka Rated™ products from you and SD. In a world full of outdoor stupidity like that awful Tincup Whiskey ad, it’s refreshing.

    • Andrew Skurka on August 31, 2016 at 8:31 pm

      Hadn’t seen that Tincup Whiskey ad before,

      Boy, that may define outdoor stupidity.

      • MarkL on August 31, 2016 at 11:51 pm

        Wow. That’s a high rate of stupid per second.

        • Yocal420 on November 30, 2020 at 8:46 am

          I like to drink whiskey and drive in pitons when I am free soloing.

  6. Rudy on September 6, 2016 at 5:09 am

    Re: “…SD believes that a tight assortment is its best hope of gaining a foothold.”

    That seems counter-intuitive. I would think restricting options such as size and color would have the opposite effect and become deal-breakers for a lot of people (of course, maybe these people aren’t your targeted audience). The “tight assortment” strategy seems more akin to the tact taken by movie studios who are unsure as to whether their new release will be embraced by the public. They release it to a small number of theatres and then wait and see how it performs before deciding their next step.

    Regarding the bag itself, I’m very intrigued. I hope these show up in REI or MEC. I’d love to try one on.

    • Andrew Skurka on September 6, 2016 at 7:14 am

      It was counter-intuitive to me, too, when I was first told about it. But it makes sense: SD’s primary “customer” is a retail buyer, not the person who eventually will use the product.

      After placing orders with their tried-and-true pack brands (i.e. Osprey), this retail buyer has only a few remaining pegs and dollars for packs from other brands. In this context, SD’s two SKU’s is more attractive than three SKU’s (S, M, L) or six SKU’s, (S, M, L in two colors, or a men’s and women’s). They can commit fewer resources to the program while still bringing it all in.

      • Rudy on September 6, 2016 at 10:12 am

        That makes perfect sense. I hadn’t thought of it from that angle. Going up against Osprey must be an uphill climb (pun intended). They have become such a monolith in the industry.

  7. sqidmark on September 8, 2016 at 3:14 pm

    I know I’m splitting hairs here but I believe that in order to address a problem you first have to properly identify it.

    Most folks, including manufactures/marketers, always point to prevention of sweaty backs as the reason for designing pack ventilation. I know that I can hike up Mt Tammany at the Delaware Water Gap without a pack and be just as sweaty as I would be with one. However, I find that I have to use packs with trampoline style suspension in order to prevent heat build up and subsequent irritation from the pack. Of course even with the trampoline I still sweat a great deal, but at least I don’t feel like ripping the pack off and throwing it on the ground after the first mile or two. So, sweat is not so much the problem as is irritation due to heat build up. Engineer from that perspective and perhaps a slightly better solution will come to light.

    I notice that the Flex Capacitor has fairly limited back contact with lots of open space. I’d be curious to see how this feels as it could to be the best alternative to trampolines I’ve seen yet.

    Hands down the most comfortable pack for me is the Atmos, and for my wife the Aura. Although I’m keeping the Atmos, it has a couple of things I don’t care for and besides I wanted something much lighter. I had purchased/returned and otherwise tried out quite a few packs, both trampoline and non. Finally settled on an Arc Haul. It’s not quite as Cadillac comfortable as the Atmos, but I can hike all day with it and it’s a lot lighter. I had it made with a Mariposa style tall left pocket for my hammock tarp, spreader bar etc.

  8. Robin on September 9, 2016 at 2:04 am

    You could solve the “stash it” pocket issue by adding an Exped Flash Pack pocket

    Perhaps Sierra Designs could make a detachable pocket as an accessory.

    • Andrew Skurka on September 11, 2016 at 8:16 am

      You could, but you will no longer be able to adjust the gusset.

      On Thurs/Fri I wore a pack with a shove-it pocket. It was nice to have, but it was no better than an easy-opening top lid. In fact, I’m tempted to say that shove-it pockets are mostly a byproduct of roll-top closures, which are a relative nuisance to open and close.

      • MarkL on September 18, 2016 at 5:05 pm

        I think it is really an offshoot of the shovel pocket on winter packs.

  9. Jennifer on September 18, 2016 at 9:33 am

    I’m finishing up my first season of backpacking ever at 56 (loving it!) and hike primarily in the California Sierra Nevada, Trinity Alps, areas where bear canisters are required. I tried a few other lightweight backpacks (ULA, Granite Gear) and chose the Exos 58 because it was the only one I could wear without feeling the bear canister uncomfortably against my back. The size small fits my 17″ torso quite well. How does the Flex Capacitor do with a bear canister?

    • Andrew Skurka on September 19, 2016 at 8:31 am

      The Flex Capacitor can fit the BV500 horizontally, but I’d recommend that you keep it vertical.

      Not sure what ULA or GG packs you were using. But in general the Flex Capacitor keeps the load further off the back. In this case, that’s a good thing, because you won’t feel the canister as much. But it’s a tradeoff — for example, most ULA packs feel more snug because they sit closer to the user.

  10. Brad on November 28, 2016 at 10:36 am

    Is there room to carry bear spray just to the rear of the hip belt pocket? It appears that there is a stabilizer strap there that might work. I would rather carry the canister on my hip than in the shoulder strap pocket. In fact, I prefer that packs have a modular design to the hipbelt pockets, but unfortunately that isn’t the direction that most manufacturers have taken. On my Exo Mountain Gear pack, I carry a removable pocket on my left side and bear spray on my right. I am anxious to see the pack up close and personal…looks intriguing.

    • Andrew Skurka on November 28, 2016 at 12:56 pm

      There might be room for a holster in the wedge between the hipbelt pocket and side pocket. Historically, I have carried mine in the side pocket (with nothing else in that pocket, so I don’t grab something else when I REALLY need my spray), but with this pack the shoulder strap pocket is very convenient.

  11. Rodney on December 31, 2016 at 4:37 pm

    Andrew, I’m very interested in this pack. My only issue so far is a sleeping pad. I have the Thermorest zLite and I see only two ways to carry it with this pack…1) Inside, though that would take up considerable room or 2) strap it to the outside. I’ve strapped it to the outside of my previous pack, Osprey Atmos 50, but I feel more secure knowing my pad isn’t secured with a piece of rope or bungee cord. Any suggestions with the Flex???

    • Andrew Skurka on December 31, 2016 at 5:08 pm

      I would first suggest at some point that you upgrade to an air pad. I know they are pricey and less reliable, but the increase in comfort is dramatic. Not sure where you backpack, but my standard summer pad is uninsulated and cost me just $40 deeply discounted, 12 oz or so.

      Now to your question. If I carried a pad on the Flex I would use the two horizonal compression straps. Not ideal but it will be very secure there. There is enough spacing between the end anchors that you could strap it on one side or on the very back. I would not worry about covering the gusset — I set it in the morning based on pack volume and forget about it until tmrw.

  12. Brad on January 16, 2017 at 1:02 pm

    Andrew, I have an 18 1/2″ torso and a 33″ waist. Do you think I would get a better fit if I picked up a Medium while there are still some left, or wait until they make the switch to S/M and M/L sizes? One issue for me is the current packs are excluded from Pro Deals, so I would not get a discount. I have no idea if the future models will be excluded as well.


    • Andrew Skurka on January 16, 2017 at 1:16 pm

      You are right on the cusp. Unless you need a pack now I would wait until the next stock arrives. SD CS will know when that is.

      Another perk: better hip belt than on G1.

      Unsure about pro deals.

      • Brad on January 16, 2017 at 1:27 pm

        Can you elaborate how the hip belt is better? I have heard it will be removable so you can switch sizes, but with my torso and waist size, I usually don’t require different sizing between the two. Are there other improvements?

        • Andrew Skurka on January 16, 2017 at 2:53 pm

          The new hipbelt is interchangeable, but it’s a more ergonomic belt. I’m going over the office later today and will try to remember to get a photo to post here.

        • Andrew Skurka on January 17, 2017 at 8:56 am

          I wrote an entire post for you about the hipbelt and about other changes to expect when this next batch arrives,

  13. Rodney on January 17, 2017 at 12:29 pm

    Andrew, I just received the pack yesterday and I think I’m going to love it. I am however, a little bummed that a new version is coming out soon. Wish I had seen this a week ago. Do you know if SD will do a swap? Or is it really unnecessary? I’m looking forward to showing off this pack on the PCT this year and will be spreading the word.

    • Andrew Skurka on January 17, 2017 at 1:38 pm

      The new batch of inventory is not a new version, and is not necessarily an improvement. For example, if your torso length is size 19, currently you are a perfect Medium. But with the new stock you will be borderline between S/M and M/L.

      As for the hipbelt, the new ones are slightly more designed, but the current one is perfectly capable. Nearly all of my experience with the Flex (e.g. testing protos, carrying out an elk) was with the current single-layer hipbelt, and I was happy with it. If you’re happy with it, too, I would run with it — the new version might fit you as well.

      No other changes were made to the pack.

      We’d love to hear how the pack holds up on the PCT. Let us know afterwards.

  14. Peter on February 12, 2017 at 5:02 am

    Andrew, Hi from Australia. This pack seems a great light-weight option in a market increasingly focused on fragile packs with harnesses incapable of handling loads above 30 lb. I assume that a good harness is worth a little extra weight for comfort even if it’s only occasionally needed for load. I’ll certainly have a look at one when I’m in the States next. A couple of questions / comments:

    1. I have an Aarn body pack (from New Zealand) which is amazing to use – even if a bit fiddly to fit. Have you tried one for comparison? The bottle pocket on the strap reminds me a little of Aarn. Any plans to put two pockets on for balance?
    2. Aarn packs are waterproof. It now seems odd to me that people buy a good pack then rely on trash bags. Any plans to make this rain proof?
    3. You commented that it’s cheaper than some other packs. I think someone focused on price is just going to walk into a store and buy an Osprey. This seems a more premium product competing against Granite Gear, ULA etc. Surely buyers would spend $50 more if better materials could make it lighter and waterproof without compromise?

    • Andrew Skurka on February 12, 2017 at 3:09 pm

      1a. Have never worn an Aarn pack. I’m aware of them, but they’re rare in the US.

      1b. You are not the first person that requested a second shoulder strap pocket. One seemed revolutionary for the US market, so I think we’re okay with that choice for now. For the second-generation, which is probably a Spring 2019 product (seems so far off!), we will certainly consider it.

      2. Aarn packs are not waterproof. Instead, Aarn packs come with removable pack liners that are waterproof. I would rather use a trash compactor bag: they’re as functional and they cost much less.

      More broadly, it’s really difficult to create a waterproof pack. For it to be truly waterproof, it must be made of waterproof fabric AND all the seams must be sealed. For a woven fabric to made waterproof, it is coated with silicone or polyurethane, which adds weight and cost, and a little bit of tear strength. But with long-term use these coatings wear off and no longer is the fabric waterproof.

      The seams are the bigger challenge, however. There are a LOT of seams on a backpack, using thick fabrics. It would be very difficult to perfectly seal all of these seems. An easier, less costly, and more reliable solution: a plastic trash compactor bag.

      3. I guess we’ll find out. So far SD is happy with the sales results, and I don’t hear anyone in the office saying that it would be doing better at $250, especially since we could not have made the pack waterproof or lighter (at least not without compromising fabric durability) with that extra amount.

      • Brad on February 13, 2017 at 9:45 am

        I would love to see a more modular design, similar to a Mountain Laurel Designs pack. That way a person could run two water bottle pockets on the shoulder straps, or two gear pockets, or one of each. Personally, I’d like to see the same for the hip belt pockets, too; although others may not agree.

        Also, it would be great if it was possible to adjust the torso length. For this pack, it looks like it would be fairly simple to have a system like Exo Mountain Gear or Stone Glacier packs where the shoulder straps attach to the back panel with velcro, giving some vertical adjustment for fine tuning.

  15. Robert on June 22, 2017 at 2:19 pm

    Another possible downside, with 30″ height it might not pass as a carry on. Anyone tried flying with one as a carry on?

    • Andrew Skurka on June 23, 2017 at 10:14 am

      I’ve flown multiple times with it as carry-on. The S/M is 23 inches tall (maybe 24 if you have it packed so full that it’s bulging out the top lid); the M/L will be more like 25 inches tall, although I don’t have one on-hand to measure it.

      It will not fit in the overhead bins on really small planes, like a 1-seat/aisle/2-seat type of plane. But most carry-on’s won’t.

  16. Robert on June 23, 2017 at 11:49 am

    Cool. Sierra Designs site for some reason has them listed at 28.5 and 30 inches respectively

  17. Brad Rogers on January 12, 2018 at 12:24 pm

    I must be in the minority, as almost all packs seem to have gone this way, but I despise stretchy water bottle pockets. I can’t get water bottles in them with the pack on, which is a deal breaker for me. I much prefer packbag material as they tend to stay “open” allowing easy use of hard sided water bottles (1L Gatorade, etc) and to me the stretchy mesh that is all the rage isn’t very durable (much less so than lenomesh or pack fabric) and water bottle pockets can see some abuse as the “corners” of the pack.

    Of course, like I said SD is not alone, The majority of packs I see nowadays have the same style stretch pockets.

    I haven’t used the Flex Capacitor, but it does seem like a novel design. The stay system is something I haven’t seen before, and the compression system, though perhaps not new (Osprey used to use a similar system), looks like it works well and is unlike anything currently on the market that I have seen.

  18. Brian V on September 2, 2018 at 4:29 pm

    I’ve just completed the WA and OR sections of the PCT with this pack. In general I like this pack for the most part, but it does have some areas where improvement is possible.


    1) Air flow: The frame and back pads really allow for excellent air flow. This was nice leaving most of my back dry and cool.

    2) Balance and freedom of movement: The frame does a great job of keeping the load centered on my back, so I felt balanced, and had a great range of movement.

    3) Adjustable Capacity: It was nice being able to go full load when hitting a town for resupply and then being able to cinch it up as I consumed provisions. With the gusset fully cinched up its a very small and nimble pack.

    4) Belt adjustments and clip. I’ve had issues in the past with belts that are hard to adjust, cinch down, or the clip wont stay locked. This belt operated flawlessly.

    5) Easy to get on and off quickly: I always felt I could easily get the pack on or off, and never felt I had to adjust adjust adjust after putting it back on, like other packs.

    Room for Improvement:

    1) The hip pockets were difficult to zip closed, and did not store much. First they would not close one handed 90 percent of the time, and it annoyed me to no end. The curvature of the underlying belt combined with the shape of the fabric makes the zipper path buckle. Using the zipper cord with your fingers/thumb at different angles for leverage would get it about 10 percent of the time. But usually to close I had to relieve BOTH hands of trekking poles or anything else, and use one hand to hold the fabric and the other to operate the zipper. Also the pockets due to the curvature of the belt and their shape would not store much and made inserting rigid items with like my camera, or my waterproof cased cell phone difficult to insert. Seems these pockets could use a little tweaking with their shape, capacity, and how the zipper works.

    2) Side pockets a bit shallow. They worked ok, but I often wished the fabric went up about another inch or two for more grip. Their relative shallowness sometimes lead to water bottles, trekking poles, or what not popping out. Also wouldn’t mind a lighter netting fabric here if possible.

    3) Lack of a security pocket inside. Distance hikers often need to store permits, id’s, credit cards, and other important documents somewhere safe. With a single compartment pack there is always lots of unpacking an repacking and Last thing you want is your most important docs in some little baggy popping out during an impromptu re-pack to get rain gear or something out. A simple small flat zipper pocket inside the pack, or maybe on the underside of the lid would be a great addition. NOTE: The lid pocket is not useful/secure for this as it will silently spill its contents if the zipper is left open and you get in the main compartment.

    4) Large size pack felt too lengthy at times. I did the shoulder to hip measurement when ordering, which indicated the large pack, and at 6ft 1 that made sense. But often when I had the pack filled with a lot of weight after a resupply, I felt the pack was really designed for someone 6ft 3. The shoulder connection seemed just a bit over my shoulders even with all adjustments cinched down. At low weights this was unnoticed and the pack hugged my back and chest and felt fine. But at high weights with the gusset spread it tended to make the pack fall back from my shoulders and throw more of the weight onto my butt. I often felt if the shoulder connectors would adjust to suck up a little more over my shoulders I would have been more comfortable with large loads.

    Here nor there:

    * I removed the camel bag holder. Its a pain to get a camel in or out if the main compartment for filing without unpacking, and doing 20+ miles a day means lots of filling. I found it just easier to carry water in hard or soft containers in the side pockets where I could refill quicker, and without always taking the pack off.

    * Would love more info on web site on how to clean and maintain the pack. Right now its so dirty and smelly from my distance hike it (and I) seem a candidate for going through a car wash!

  19. Gerald on October 10, 2018 at 3:06 pm

    I am interested in this pack. However, I always carry my small mirror less camera and access it quickly by putting it in the brain of my Gregory pack. Works well and I don’t need to take the pack off. Would this top pocket accommodate a small mirror less camera with lens? Thanks

    • Andrew Skurka on October 10, 2018 at 3:43 pm

      No, the pocket is too small.

      In general, you’d have better access to the camera (and can take more photos) if you used a shoulder mount like this one,

      • Gerald on October 11, 2018 at 9:28 am

        I’ve owned one before. It seems to work with some people, but it’s very uncomfortable for me. Thanks for the reply Andrew!

  20. Joe Abraham on June 10, 2019 at 11:50 pm

    Hi Andrew, congratulations on the design and success of the pack. Just to confirm, so none of the materials in the backpack have any DWR or PU or any other waterproofing coatings on them? When I called up SD, they thought there was a PU coating. Thanks, Joe

    • Andrew Skurka on June 12, 2019 at 3:51 pm

      SD customer service would know best. Honestly, I can’t recall, I have not been with SD for 1.5 years.

      DWR won’t do jack. It’s very vulnerable to abrasion.

      PU or silicone adds strength, but eventually breaks down.

  21. Lin on July 28, 2020 at 8:39 pm

    How much weight can the 40-60 pack carry?

  22. Caleb H. on July 25, 2021 at 10:06 pm

    Andrew stated in the release video for this pack that he personally tested it with a 70 lb. load. He also stated that though he never recommends anyone carry 70 lbs., he was surprised at how well the pack handled the load. Hope this helps.

  23. Martin Kuster on February 4, 2024 at 2:04 pm

    I think the bottom panel of the pack should be made of a thicker/more durable material. I have used the pack on 30 days distributed over several backpacking trips and the pack now has tears and several holes in this panel. This obviously comes from scraping over rocks and fallen trees, especially when a hard sided bear canister is in the pack. Sierra Designs considers it normal wear and tear but the durability seems worse compared to my Osprey and Deuter packs that have seen much more use and abuse. On top, Osprey replaced my completely worn out Aether for free when I asked them, at my cost, to replace the buckle on the hip belt.

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