Sierra Designs FLEX CAPACITOR 25-40 BackPack Birch

Meet the pack that does it all. The Flex Capacitor family of packs feature adjustable volume to handle both short and long hauls, and a Y flex suspension system that carries above their weight class. With three sizes in a 25-40, 40-60, and 60-75 L capacity, there is a flex pack to fit your needs. A bucket lid with a stash pocket closes everything up, while dual stretch pockets on the shoulder straps and side of pack cover shove it needs.

Our thoughts:

I used the Sierra designs Flex capacitor on my 350 kilometer thru-hike coast to coast in Scotland. I often carried around 10-14 kilos in the backpack and had a daily distance of between 25-40 kilometers. I started the trail liking the backpack, and finished the trail loving it. What I thought at first would just be a gimmicky backpack turns out to be a highly thought out piece of gear. Everything from strap placement to internal frame and lumbar support – this pack is a highly engineered marvel at a price point that doesn’t break the bank.

I love the design of the Sierra designs Flex Capacitor – it works, and works great. I have had loads of up to 30 kilos in this backpack and was amazed at how well it carried the weight. Granted, I hate carrying 30 kilos and see no reasonable excuse to do so, but just the thought that the pack can carry it amazes me for such a lightweight backpack. Nothing on this backpack seems like it was done on a whim – it shows that a lot of effort and time was put into the pack by very knowledgeable hikers. This is not immediately noticeable until you actually start using the Flex Capacitor.

On my walk through Scotland I marveled at how well the bag felt, I don’t know if I’ve ever used a more comfortable and stable backpack. Great ventilation on my back kept me from sweating too much, and the bag always worked when I needed it to. I honestly can’t think of anything negative to say about this backpack.  

• Excellent design and function
• Great carrying capability
• Excellent frame design
• The ability to easily adjust from 40 to 60 liters
• Lightweight
• Everything on the bag has a use
• No detail left to chance
• Big useable hipbelt and side pockets
• Water bottle holder on the Chest strap is genius

• I would have really liked to see a little bit taller pack – it’s just on the edge of being too short for my long back
• At 1.2 kilos it might be on the heavier side. But again, you get a great frame for the weight

 

Features:

• Expandable Volume
• 2 stretch mesh side pockets
• 2 stretch mesh hydration pockets on shoulders
• Zippered hip belt pockets
• U-shaped top acces zipper
• Small stash pocket in lid
• Ultralight weight
• Lightweight ‘Y’ Flex DAC suspension

Materials:

• 100D Nylon-Poly Ripstop/420D Nylon Oxford

Tech specs:

• Capacity: 25-40L / 1525-2440 in³
• Weight with S/M waist belt: 2 lbs 7 oz  /1.1 kg
• Weight with M/L waist belt: 2 lbs 8 oz / 1.13 kg
• Torso Fit: 16″ – 19″ / 40.6 – 48.3 cm
• Hip Fit with S/M waist belt: 29″ – 32″ / (74 – 100 cm)
• Hip Fit with M/L waist belt: 32″ – 35″ / (82 – 115 cm)
• Dimensions (H x W x D): 23″ x 11″ x 8.5″ / 58.4 x 28 x 21.6 cm
• Suspension: Y Flex DAC