Take a quick ride on your mountain bike with all the essentials packed in Osprey's Viper Hydration Pack. This small, streamlined backpack has enough room for your helmet, pump, tube repair kit, and the included Hydraulics LT 2. 5L reservoir. The LidLock system secures your helmet when you're not on your bike. Osprey made this pack with well-ventilated Airscape and BioStretch mesh, and the back panel has an Atlion foam framesheet to enhance stability without interfering your mobility on the mountain.