The Camelbak HydroBak Hydration Pack is a versatile pack ideal for all sorts of activities. The low-profile, comfortable design of the HydroBak keeps the pack stable during your rides and doesn’t interfere with your helmet. An external zip pocket is just the right size to hold your essentials, like a set of car keys or an energy bar. The reflectivity of the HydroBak has been increased for low-light visibility. With a 50 oz Antidote Reservoir, the Camelbak HydroBak Hydration Pack carries enough hydration for 1 to 2 hour outings. You won't find a better way to drink on-the go than the CamelBak HydroBak Hydration Pack.