The Osprey Viper 13 is the largest of the Viper Series with 800 cubic inches of storage capacity, a decent amount for sure. It’s big enough for many day-long rides yet small enough to be considered a marathon pack. With the proven 3L large mouth Hydraform bladder you get one of the best bladders on the market plus key compartments to help you organize your gear. The large hose and decent bite valve on the included bladder both work great and the reservoir didn’t leak on me. The bladder, which I can’t rave about enough, works, fits, and cleans well. The molded form ensures that even if filled to the brim with water, you don’t feel like there’s a salami on your back.