The Osprey Men's Siskin 8L Backpack is a hydration pack for mountain biking. Slim but capable, this pack won't drag you down, yet still offers plenty of space for essentials. The streamlined style hugs the body to reduce drag while zipping around the trails, and the included Hydraulics LT 2.5L reservoir keeps thirst quenched along the way. Space for tool organization, snacks, a rain shell, and more allows you to spend all day biking your heart out.