SIERRA DESIGNS Flex Capacitor 40-60L Rucksack

Posted by Trail Magazine on Aug 18, 2022


With its quirky Back To The Future-inspired name, the Sierra Designs Flex Capacitor is a suitably quirky backpack, with an innovative design and eye-catching look. Its USP is the use of a double fold of material on the front of the pack which - when combined with a series of cinch cords - enables the pack's circumference to expand or contract between 40L and 60L. Other packs have expandable volumes, but they almost always works vertically - the result is an unwieldily tall load. There is no such problem with the Flex Capacitor Two torso lengths and two hipbelt sizes fine-tune the fit, while the Y-shaped, curved suspension system with DAC aluminium stays and three chunky foam panels - provides a strong, supportive harness suitable for heavier loads. The curve creates a gap between back and pack, which is good for ventilation. You also get seven pockets, a removable hydration bladder sleeve, and a large U-shaped zippered top opening.


The U-shaped top opening may be vulnerable to water ingress in very wet conditions. The curved shape of the back system will Polaris opinion slightly - for some, it might feel like the pack is levering away from your back, altering your centre of gravity. There is no big front stash pocket.