Sierra Designs Flex Capacitor 40-60L Backpack


Torso Size


The Flex Capacitor is a robust backpack designed with lightweight durability and adjustability in mind. Its expanding horizontal gussets offer 15-20L of additional capacity for longer backpacking trips, or can be cinched tight for more compact loads. For added convenience, multiple quick-stash solutions on the straps, sides, and lid give you plenty of spots to store mid-trail necessities. And the Y-Flex suspension adds extra support, so this lightweight pack has more capacity than meets the eye.

  • Features

    Lightweight Y-Flex Suspension provides superior increased support.
    20L adjustable volume to tailor both to extended backpacking trips or shorter day trips.
    Hydration sleeve doubles as removable summit sack.
    Dual adjusting shoulder straps tailors pack fit to your torso.
    2 hydration pockets on shoulder straps.
    2 stretch mesh side pockets to keep essentials close at hand .
    Zippered hip belt pockets for easy storage.
    U-shaped top access zipper for easy access while backpacking.
    Lightweight backpack.

  • Specifications

    100D Nylon Honeycomb/420D Oxford

    S/M Torso

    Capacity: 40-60L / 2441-3661 in3
    Weight: 2 lbs 12 oz / 1.23 kg
    Torso Fit: 16" - 19" / 41 - 48 cm
    Hip Fit with S/M waist belt:
    Dimensions (H x W x D): 25" x 12.5" x 12.5" / 63 x 20 x 32 cm
    Suspension: Lightweight Y-Flex

    M/L Torso

    Capacity: 40-60L / 2441-3661 in3
    Weight: 3 lbs 2 oz / 1.4 kg
    Torso Fit: 18" - 21" / 46 - 53 cm
    Hip Fit with M/L waist belt:
    Dimensions (H x W x D): 27.5" x 8.5" x 12.5" / 70 x 22 x 32 cm
    Suspension: Lightweight Y-Flex

  • What We Think

    Sierra Designs as per usual has come up with another innovative design in the form of an adjustable volume backpack, meaning you can have a backpack for an overnight or week long trips, simply by adjustment of straps tightening a gusset which cinches the Flex Capacitor down, so everything remains stable on your back.

    There is a nice airflow through the gap created by the Shoulders and Lumber pads, to keep you cool during hot weather.

    Designed by Andrew Skurka, the well known long distance backpacker. Watch the video above from Andrew to get a good fell for all the features and benefits. The Flex Capacitor Backpack carries very comfortably even with heavier loads where many packs would feel uncomfortable and unstable .