New release: A pack for the future

The Sierra Designs Flex Capacitor 40-60 Pack is now available for pre-order. Expected ship date is October 4.

If you are a regular reader of this blog, you’ve been hearing about the Flex Capacitor for months. If you need to get caught up, here is some recommended reading and viewing:

The Flex Capacitor is currently available only from Visit the product page for key specs and sizing information. It is available in three torso length sizes: S, M, and L. The hipbelts are proportional for each size, but they are interchangable for those whose proportions are atypical. In that case, contact SD before the ship date so that your pack can be shipped with a correctly sized hipbelt.

Overall, I am very satisfied with how this pack turned out, and delighted to have my name attached to it. For 2.5 pounds, it offers a lot, in terms of versatility, load carrying, and features. The price is also very competitive, at just $200.

If you have any questions about the Flex Capacitor, leave a comment. I’d be happy to answer it.

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

Posted in on September 25, 2016


  1. John Abela on September 25, 2016 at 12:56 pm

    Congratz on getting this brought to market Andrew!

    • Chris Sikuq on September 26, 2016 at 1:09 pm

      John Abela,

      You and Andrew Skurka are my two most trusted sources for outside gear and tips. It does matter to me what you two say. Thanks to both of you.

  2. Lesley on September 25, 2016 at 4:50 pm

    Liking the pocket areas.
    Not too sure about the zip lid re waterproofing!
    I do like the flip over lid with front clip on mine, I feel it’s more protected ….
    I like the side pockets for easy access to camer, money etc ….
    Over all it looks the biz ??

    • Andrew Skurka on September 25, 2016 at 5:11 pm

      Re waterproofing, my universal recommendation — regardless of the backpack — is using a 20-gallon Brute Super Tuff trash compactor bag as a pack liner. Most packs are made of waterproof fabric, like the Flex, but without sealed seams they will leak in heavier and extended rain.

  3. Andy Cheng on September 25, 2016 at 5:45 pm

    I am from Taiwan, will the The Flex Capacitor ship to Taiwan?

  4. Bud on September 26, 2016 at 4:02 am

    How comfortably does the pack carry weight in the mid and upper twenties? I ask because it doesn’t seem that the Y-flex suspension system could replace the comfort associated with true frame-style backpacks.


    • Andrew Skurka on September 26, 2016 at 6:52 am

      Mid- and upper-20’s, absolutely no problem, carries like a dream. On a trip last week I left the trailhead with 31 (we weighed it) and that load was well under its capacity. I tested one of the prototypes to 70 pounds, while hunting last fall. I would NEVER recommend carrying this much weight because it is crippling, but I was very surprised by how well the pack carried it. That Y-FLEX stay is very stiff vertically, and it anchors directly into the hipbelt.

      • Bud on September 26, 2016 at 9:51 am


        Thanks for the quick response! One more question though: would the compression straps be a feasible and good solution for holding snowshoes to the pack?

        Thanks again!

        • Andrew Skurka on September 26, 2016 at 10:00 am

          Yes, that is one of the exact purposes for which they were designed.

  5. Tor Ivan Boine on September 26, 2016 at 4:51 am

    If it only had a quick access on the back (against your back) like F-stop gear has. Granted, they are aiming at photographers, but I just love that quick access.

    Btw, I watched your “how to pack” video. That was a small sleeping bag and tent! I assume you have a page with an overview of your camping gear?

    • Andrew Skurka on September 26, 2016 at 6:49 am

      My gear selections are determined by (1) my trip objective and (2) the conditions. By trip objective, I mean the ratio of hiking versus camping; I pack less if I’m doing more of the former, and more if the latter.

      I’m slowly picking away at a long list of gear lists that I’d like to post to my site,

  6. Chris Sikuq on September 26, 2016 at 1:01 pm


    I like your videos on the Flex Capacitor 40-60 Backpack. I just placed a pre-order for the large version using the link from your website to Sierra Designs.

    Please note, there was an extra charge of about $7 for shipping USPS to my address in Alaska, hardly free shipping as advertised.

  7. Eric S on September 26, 2016 at 2:04 pm

    Do you have any suggestions on how to carry a Therm-a-rest Z Lite Sol sleeping pad with this pack? With my current setup (Osprey Aether) I can strap it to the bottom of the pack with two buckles but the Flux Capacitor doesn’t seem to have those kind of straps on it.
    Also, once the pack is released I’m assuming it will be available at retailers (I’d like to try one on)?

    • Andrew Skurka on September 26, 2016 at 4:54 pm

      A few suggestions:

      1. Funds permitting, I would recommend upgrading to an air pad. I used closed cell foam for many years, usually the RidgeRest, and still do during the winter. However, air pads are much more compact and much more comfortable; the weight difference is negligible, especially when sleep quality is considered.

      2. Cut the Z-Rest to torso-length, and use your pack to insulate your lower legs. This will make the pad much more packable, to the point that you can get it inside your pack possibly.

      3. If you really want to strap it on the exterior of the Flex Capacitor, use the horizontal compression straps. There should be enough slack to make it work, especially if you have the main compartment somewhat collapsed via the adjustable gusset.

      Re availability, it depends on what retailers pick it up. It probably will be specialty retailers only, not REI. If you can’t find it locally, buy it, try it out, and return it if you don’t like it. You’ll be out some postage, but unfortunately that’s the way it is with the disappearance of small brick-and-mortar retailers.

  8. Chris on September 27, 2016 at 4:45 pm

    Andrew- Love your website!
    Knowing you have used many different packs, if you were to buy just one lightweight pack to do it all- 2-3 night trips and 7 day trips- is this the pick you would buy?

    • Andrew Skurka on September 28, 2016 at 9:39 pm

      I’m biased, of course. But, yes, I think the Flex Capacitor is a very strong candidate for the uses that you described. The FC has a better range than most packs, because of the adjustable volume. For me, when it’s collapsed it’s a 2-4 night pack; and when it’s open, I can use it for about 1.5 weeks. With my other packs, they for 2-4 nights or 7-10 nights, not both.

  9. Chris Sikuq on September 30, 2016 at 5:38 pm


    They shipped my Flex Capacitor! Can’t wait.

    Question: I always use the left side shoulder strap for bear-spray/water-holders as I first insert my left arm into the shoulder harness and then enter my right arm harness last, when lifting up the backpack. I notice that in the video you always enter your right hand first. With just one bottle holder, how did you decide its current right side placement? My preference would have been using my left arm strap for the bottle holder. I’m right-handed.

    • Andrew Skurka on September 30, 2016 at 7:18 pm

      Six of one, half dozen of the other.

      The right-side pocket seems a little bit easier to access for a right-handed person (which I am, too). And because of the way that I put it on, whereby I lower it down rather than throw it across, the straps don’t get tangled, so it was never a problem.

  10. Jack Brauer on October 10, 2016 at 9:42 am

    Hi Andrew, I just wanted to mention that I purchased a Flex Capacitor pack after reading about it here. I knew that a pack you helped design would be a good one, and sure enough, this pack kicks ass! It rides so well on my back; doesn’t pull back on my shoulders whatsoever. And the volume adjustment feature is so cool.

    I also have an Osprey Exos 58 pack which I’d say would be one of this pack’s closest competition, being similar weight and volume. The Exos rides well also, however the big difference for me is that the Flex Capacitor is SO much easier to get into, with only one top zip versus all the clips and cinches of the Exos. This is a big deal for a photographer like me, when having to access a small camera case in the backpack.

    The only minor improvement I’d like to see would be a V-shaped compression strap on the bottom of the pack. Because the pack’s so light, I will be using it as my go-to day pack; however, with a small load there’s not a good way to compress the very bottom of the pack and keep the weight up higher.

    Anyhow, overall I’m super stoked on the pack! Great job!

  11. dgray on November 27, 2016 at 4:47 pm

    Can a BV500 fit in the pack horizontally when the pack is expanded?

  12. Alex on September 4, 2017 at 2:55 pm

    Hi Andrew, is it feasible to use the pack as carry-on? I had this funny idea that I could pull the suspension, and either repack the pieces or use a foam pad like a Z-Lite Sol as a framesheet. But I imagine that it would cause the top to sag substantially, or maybe I’m just trying to cram too many use cases into a single pack.

    • Andrew Skurka on September 6, 2017 at 1:50 pm

      I have used it for carry-on several times. It doesn’t work on very small planes, but on the standard 737 it’s fine. I use the S/M, however, and the M/L would be tighter (because it’s 3 inches taller). If you do need to collapse it, the suspension can be disassembled quickly so that it’s longer full height.

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