Reader Q: Can a bear canister fit horizontally in the Flex Capacitor?

The Flex Capacitor loaded with a BV500, about 6 inches from the bottom on top of sleeping bag and pad.

A question from reader, Scott F:

Will a Bearikade Weekender canister fit horizontally in the Sierra Designs Flex Capacitor 40-60 Pack?

To this specific question, my answer is: I don’t know for sure, but it should. I don’t own a Bearikade so I have not tested its compatibility, and I don’t recall any guided clients last year with both a Flex and a Bearikade.

However, I know that the BearVault 500 (which I own and which is similarly sized) will fit horizontally inside the Flex Capacitor when it’s fully expanded. I keep it about 6 inches from the bottom, sitting on top of my sleeping bag and pad, even though this is the narrowest part of the pack (because of the curvature of the Y-shaped stay). If loaded higher in the pack, it fits even better, with no tension on the pack body.

The BV500 fits horizontally into the Flex, with some room to spare.

The BV500 slides in and out easily of the Flex — it’s not a fight. And it has no adverse effects on the pack: the side pockets and compression straps remain fully functional, and there is no change in its load-carrying ability or its back panel shape.

The only minor issue is that the canister will place disproportionate tension on the pack body — the main compartment is shaped more like a half-cylinder than a rectangle, and therefore doesn’t have “corners” that match those of the canister. Just be careful of abrading the pack where the top or bottom of the canister is pushing hardest against the fabric.

Beware of abrading the pack body where the canister is pressing hardest against the fabric.

The Bearikade Weekender is slightly smaller than the BV500, especially in the length:

Based on the fit of the BV500, I will speculate on how several other popular canisters will fit inside the Flex Capacitor:

When considering the suitability of a backpack for trips on which canisters are required, the “Does it fit?” question is an important one. But I think it’s equally necessary to ask, “How well does the pack carry with a canister?” Canisters add weight and bulk, and many otherwise nice packs perform poorly when loaded with this item. More specifically:

  • If a pack has too little volume, after inserting the canister there is little room left for anything else;
  • If the pack is too narrow, the canister alters the shape of the pack, possibly creating a “bulge” against your pack or putting excessive pressure on delicate stays; or,
  • If the pack is not designed to carry heavier loads, it becomes uncomfortable to wear.

In this regard, I think the Flex performs exceptionally well. On multiple trips last year I loaded the Flex with up to 40 lbs, including a full BV500 and sometimes guide gear or an ice axe. To finish the season I carried out 70 pounds of elk meat. While the Flex is 8-16 ounces heavier than the bulk of “ultralight” packs, it carries weight better than perhaps all of them.

At the end of a 9-day yo-yo of the Pfiffner Traverse. At the start, my pack weighed in the low-30’s, including a fully BV500 and an ice axe.

Questions about bear canisters or the Flex? Leave a comment.

Disclosure. I strive to offer field-tested and trustworthy information, insights, and advice. I have no financial affiliations with or interests in any brands or products, and I do not publish sponsored content

This website is supported by affiliate marketing, whereby for referral traffic I receive a small commission from select vendors like Amazon or REI, at no cost to the reader. As an Amazon Associate I earn from qualifying purchases.

Additional disclosure: I co-developed the Flex Capacitor with Sierra Designs. I have been honest about its shortcomings. Overall, I think it’s an excellent product.

Posted in on January 3, 2018
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  1. Hunter G Hall on January 3, 2018 at 11:21 am

    I have a Bearikade scout and can tell you it fits OK (not great) in a smaller 52 liter pack (Zpacks ArcBlast).

    I had to fiddle with it, but it fits best vertically lower in the pack, about where Andrew puts his. I wrap it in clothing I don’t need during the day and it works great.

    The diameter of the Scout and Weekender is the same, the only difference is height. I had the weekender originally and it did NOT fit in the ArcBlast at all horizontally, which is why I switched, but still carry it vertically now since it’s more comfortable and won’t damage the pack with friction.

  2. Daniel Postilnik on January 5, 2018 at 4:49 pm

    I carried a BV500 in a Flex Capacitor on a 3-day/2-night trek that was partially ultralight (my wife was with me) and it fit just fine, so I can second Andrew’s report.

  3. Dani on June 20, 2018 at 2:55 pm

    This may sound dumb but here it goes. Why do the manufacturers of Bear resistant containers make the container is this shape? Why not make one specifically for backpack, long-trip hikers? I am a petite hiker and would like to see a container for women 5′ and under. Your thoughts?

    • Andrew Skurka on June 20, 2018 at 3:16 pm

      The most efficient shape would be a sphere, in terms of maximizing volume per surface area. But a sphere is not very user-friendly (hard to pack, rolls way easily, no natural place to put an opening) so they go with a cylinder instead. A box would be more user-friendly than a cylinder, but I don’t think it’s as strong of a shape all things being equal, so heavier materials would have to be used to avoid destruction.

      There are some smaller canisters that might work better for you. Refer to this page for details,

    • Burk on July 23, 2018 at 1:17 am


      It’s not a dumb question, but there is a good, satisfying answer! The main reason that bear canisters are 1) cylindrical and 2) have a minimum diameter — despite not fitting great in a pack — is because a bear would be able to jaw-crush an oblong and/or smaller size container.

      A cylinder of a certain size is basically the best compromise shape between “does it fit in your pack” (yes) and “can a bear fit its teeth around it” (no). Anything else would require heavier materials, as Andrew mentioned.

      Source: long time backpacker, bear avoider, and REI employee. 🙂

    • Ken on November 20, 2023 at 1:35 pm

      Yeah, for instance, a half cylinder? D

  4. James Johnston on May 19, 2019 at 5:47 am

    Any idea how well an Bearikade Expedition would fit on this pack? 9″ diameter base by 14.5″ length

    • Andrew Skurka on May 19, 2019 at 6:33 am

      The BV500 is 12.7 inches long, or 1.8 inches shorter than the Expedition. I don’t have one handy, but my recollection is that the BV500 swallowed the Flex horizontally, with room to spare. If you can’t get the Expedition to fit horizontally, you can most definitely put it vertically, as most other packs will require you to.

  5. Brittany on April 5, 2021 at 7:46 am

    I just ordered a 40-60 Flex for can country…my question is do you “open” the pack where the can is and keep it “closed” nearer the top? Or should you strive to keep the pack a cylinder (vs a bottom heavy cone)? I hope this question makes sense.

    • Andrew Skurka on April 5, 2021 at 12:27 pm

      The question doesn’t really make sense, but let me try to answer it.

      With the Flex, the pack is wide enough (when not compressed) to put most canisters horizontal. This is the ideal orientation because it’s easier to pack everything else. My recommendation would be to put your sleeping bag and perhaps a few other soft nighttime items at the very bottom (e.g. pad, bivy, tarp/fly). Put the canister atop this layer, up against your back. The gap between the canister and the outside of the pack may be large enough to stuff something in there, but be careful — if you really stuff it in there, the canister is going to start putting pressure on your back, which you want to avoid.

      Everything else goes above the canister.

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