The foundation of the versatile Flex Capacitor is Sierra Designs' unique patent-pending gusset system. This gusseted interior fabric, combined with an array of compression straps allows the pack to expand from 40 to 60 litres effortlessly, allowing you to carry more or less, depending on your exact needs at the time.
Unlike conventional backpacks that expand vertically to house more equipment, the Flex Capacitor expands around its circumference, which in turn provides a more stable carry as it doesn't affect the pack's centre of gravity. The expanding design allows you to carry all of the food and essentials for a multiday trip, and as you diminish your supplies it can then contract to reduce excess volume for greater stability. The smaller size of 60 litres is ideal for a fast day hike, while the additional 20 litres expansion can easily accommodate tents and overnight gear for longer adventures.
The lightweight Y-Flex suspension system provides rigidity vertically, whilst providing torsional flexibility to work with your body’s movements without causing the load of the pack to collapse. There's also a handy u-shaped zippered top lid that allows easy access to the main body of the pack.
The back system of the Flex Capacitor 40-60L is comprised of two scapular and one lumbar pad. This promotes airflow around the lower back for warm and humid conditions. Opting for a significantly simpler back system makes this pack super-lightweight.
Dual adjusting shoulder straps allow you to tailor to a perfect torso fit, and those straps also contain two hydration pockets. There are two further mesh pockets on the side, with zippered hip belt pockets to boot. So you'll never struggle to find nooks to pop in those essentials you know you'll need quick access to.
Tailor-made for those who want options out on the trail, the Sierra Designs Flex Capacitor is a revolution in the pack world and is perfect for both day hikers and wild campers alike.
Hydration System: Hydration sleeve doubles as removable summit sack
Pockets: 2 hydration pockets on shoulder straps, 2 stretch mesh side pockets to keep essentials close at hand, Zippered hip belt pockets for easy storage
Features
Lightweight Y-Flex Suspension provides superior increased support
20L adjustable volume to tailor both to extended backpacking trips or shorter day trips
Dual adjusting shoulder straps tailors pack fit to your torso
U-shaped top access zipper for easy access while backpacking
Tech Specs: 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: 29" - 32" / 73.7 - 81.3 cm
Dimensions (H x W x D): 25" x 12.5" x 12.5" / 63 x 20 x 32 cm
Tech Specs: 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: 33" - 48" / 84 - 122 cm
Dimensions (H x W x D): 27.5" x 8.5" x 12.5" / 70 x 22 x 32 cm
V2
The Lowdown
Material Body: 100D Nylon-Poly Ripstop/420D Nylon Oxford
Hydration System: Not Compatible
Pockets: 2 stretch mesh side pockets, 2 stretch mesh hydration pockets on shoulders, Zippered hip belt pockets, Small stash pocket in lid
20L adjustable volume to tailor both to extended backpacking trips or shorter day trips
Dual adjusting shoulder straps tailors pack fit to your torso
U-shaped top access zipper for easy access while backpacking
Tech Specs: S/M Torso
Capacity: 39-56L / 2380-2440 in3
Weight with S/M waist belt: 2 lbs 9 oz / 1.16 kg
Weight with M/L waist belt: 2 lbs 10 oz / 1.19 kg
Torso Fit: 16" - 19" / 40.6 - 48.3 cm
Hip Fit with S/M waist belt: 26" - 38" / 66 - 97 cm
Hip Fit with M/L waist belt: 33" - 48" / 84 - 122 cm
Dimensions (H x W x D): 27.5" x 11" x 10" / 70 x 28 x 25.4 cm
Tech Specs: M/L Torso
Capacity: 42-60L / 2563-3661 in3
Weight with S/M waist belt: 2 lbs 9 oz / 1.16 kg
Weight with M/L waist belt: 2 lbs 10 oz / 1.19 kg
Torso Fit: 18" - 21" / 45.7 - 53.3 cm
Hip Fit with S/M waist belt: 26" - 38" / 66 - 97 cm
Hip Fit with M/L waist belt: 33" - 48" / 84 - 122 cm
Dimensions (H x W x D): 27.5" x 11" x 10" / 70 x 28 x 25.4 cm
Reviews
Neil
21/03/2024
Perfect pack for my use love the way you can expand it if required
Front pockets are brilliant I can get to everything I need without having to stop
Calum
04/03/2024
So happy with this backpack. Great fit, light and really like the expansion option. Tested it out over a 2 day trip and I'm now looking forward to a 4 day trip to test it with more gear in.
Tim
17/02/2024
The flex system works really, really well, the sac is lightweight for its capacity and very fair value for money. Have used it in Patagonia carrying over 15kg per day for multiple days and it was as comfortable as you could hope in the circumstances.
The hip belt is able to take most of the load and create some airflow for the back.
Overall this pack is exactly what I hoped for and wanted. The zip closure on the lid could be a little better and the top pocket a little bigger, but in the grand scheme of how well it delivers on weight, space flexibility and carrying comfort I wouldn’t mark it down for those small points at all.
Raymond
30/01/2024
Great size for taking all the gear for a shrt wild camp. Very comfortable and sturdy.
Chris
26/11/2023
The flex capacitor rucksack is perfect for wildcamping
Sierra Designs
Sierra Designs gives you a range of high-quality outdoor equipment, crafted around the principle of function, style and affordability