Osprey Raven 4 Hydration Lumbar Pack – Black. Off the back and leading the packOspreys premium mountain bike lumbar includes a 1.5-liter reservoir and features designed to keep you in the saddle. Dual hipbelt pockets grant easy access to snacks and a stretch mesh front pocket keeps kneepads gloves or a light jacket handy. Side compression and a womens-specific fit on the Raven 4 stabilize the pack from techy climbs to the jump line.