The dakine session 12l hydration backpack the session 12l bike hydration backpack is a full featured pack combining the cooling comfort of a breathable back panel with airy shoulder straps this narrow lightweight pack features a 2 liter vertical hydration reservoir with a bite valve the pack offers plenty of storage including an organized front pocket a fleece lined sunglass pocket additional side pockets plus an external helmet carry system the session is a do it all bike pack to keep yo