Water sustains you, but you don't always need to carry a full 3 liters of it. Each liter tips the scales at 2.2 pounds. Why carry 6.6 pounds and a pack big enough to transport it when you can make do with less? Less weight means more of your bike's power can be devoted to going fast. Less bulk means you're more limber for exerting better body English with less fatigue. The OGIO Erzberg 35 Hydration Pack keeps you fueled with 1 liter (35 oz) of fluid and the pack hugs you tight like a bionic organ that's a part of you.