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  • Sierra Designs - Flex Capacitor 40-60L Backpack - Jet Gray
    Sierra Designs - Flex Capacitor 40-60L Backpack - Detail
    Sierra Designs - Flex Capacitor 40-60L Backpack - 3/4 Back
  • Sierra Designs - Flex Capacitor 40-60L Backpack - Jet Gray
  • Sierra Designs - Flex Capacitor 40-60L Backpack - Detail
  • Sierra Designs - Flex Capacitor 40-60L Backpack - 3/4 Back
Sierra Designs - Flex Capacitor 40-60L BackpackView Larger Image

Sierra Designs Flex Capacitor 40-60L Backpack

25% Off
$149.99 $199.95

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    • Jet Gray,S/M Bag / S/M Hip Belt
      sale $149.99
    • Jet Gray,M/L Bag / M/L Hip Belt
      sale $149.99
    • Jet Gray,S/M Bag / XS/S Hip Belt
      sale $149.99

    Tech Specs

    [body] 100D Nylon-Poly Ripstop, [bottom] 420D Nylon Oxford
    40 - 60L (2441 - 3661cu in)
    Y-Flex (DAC pressfit aluminum)
    Shoulder Straps:
    yes, padded
    Waist Belt:
    yes, padded
    Hydration Compatible:
    top, U-shaped zipper
    2 zippered waist belt, 1 zippered top lid, 2 side stretch mesh, 1 strap bottle
    Ice Axe Carry:
    Trekking Pole Carry:
    Weight Capacity:
    35 - 50lb
    30 x 13 x 10in
    Claimed Weight:
    2lb 11.2oz
    Recommended Use:
    Manufacturer Warranty:

    Great Scott!

    No, you might not be able to travel through time using this pack, but there's a good chance it's a gift from the future. The Sierra Designs Flex Capacitor Backpack can expand and compress throughout your trip as your needs change, and it does so with lightweight stability. A unique gusset system on the back lets you enlarge the bag to 60 liters at the start of your trip, then tighten it down to 40 liters as your food reserves dwindle and you've moved layers from bag to body.

    Whether your trip last two days or seven, you'll be glad for all the places to stash your stuff, thanks to seven different pockets as well as loops on the back for your ice axe. If you're trekking through uneven terrain or might encounter snow, the compression straps can help keep the necessary tools attached, waiting and ready for deployment. A zippered stash on the top of the bag is a perfect hiding place for the vitals you'll need throughout the day, and there's even a spot for your reservoir should you get thirsty.

    • Versatile pack for short and not so short adventures into the wild
    • Can expand in capacity as you pack and unpack throughout the trip
    • Durable ripstop construction fends of sharp rocks and branches
    • Y-Flex internal suspension provides torsional load bearing support
    • Raised lumbar and scapula pads provide comfort and air flow
    • Compression straps can secure snow shovels and trekking poles
    • Mesh pocket on shoulder strap for easily accessible water bottle

    Very happy with my Flex Capacitor

    • Familiarity: I've used it several times

    I purchased my Sierra Designs Flex Capacitor backpack from Backcountry prior to embarking on a 6 day hike of the famous 'Overland Track' in Tasmania, Australia. I was very happy at the performance of the backpack. It stabilised the load very well with the compression straps, and was comfortable and firm to wear. At the end of each day, my back was not sore. It was easy to access with the zip. I liked being able to compress it in further as I ate my way through my food over the hike. I highly recommend this backpack. I love that it works well for weekender getaway hikes as well as multi-day hikes. In fact this backpack will virtually every trip, due to its capacity to expand from 40L - 60L. It's also very light for the load capacity it will handle. No regrets. Recommended.

    Hip Belt Sizing Help

    • Familiarity: I gave it as a gift but have feedback to share

    Does It All

    • Familiarity: I've put it through the wringer

    I love that this pack can do pretty much anything. I mainly do quick weekend trips but wanted to have a pack that can do the occasional longer backpacking trip.

    This is such a simple pack that it has even worked well for travel.

    Super Innovative Pack!

    • Familiarity: I've used it several times

    The innovation in this pack is truly incredible. I love that it can expand between 40L-60L, which makes it super versatile. No need to have a weekend pack and a separate pack for weekend+ adventures. The Flex Capacitor can meet the demands of both without really adding weight. Nice work Sierra Designs!

    Admiring the view!

      Admiring the view!

      How to fit the Flex Capacitor

        Flex Capacitor review w/ Andrew Skurka

          Check out this great video with Andrew Skurka discussing the thoughts and details behind the Flex Capacitor 40/60 pack.

          Sierra Designs

          SizeS / MM / L
          Torso Fit Range

          16 - 19in

          (41 - 48cm)

          18 - 21in

          (46 - 53cm)