Mountain bikers, rejoice, for Osprey has crafted a hydration pack for the hills, jumps, and drops we traverse. The Siskin 8L Backpack is a small, lightweight pack engineered for comfort on our biggest rides, thanks to breathable next-to-body components and an included 2. 5-liter reservoir. The Osprey Hydraulics LT stashes in its own space, leaving loads of room in the main compartment for our on-trail necessities: tubes, a hand pump, an extra jacket, and more.