OSPREY Hydraulics Lumbar 1.5 Res Red O/SOspreys Hydraulics LT 1. 5L Lumbar Reservoir by Hydrapak is made for those who prefer an off the shoulder hydration solution. Designed to fit in most lumbar packs, but perfectly pairs as an extra or replacement reservoir for Osprey's Seral lumbar mountain biking pack. Twin welded chevron baffles stabilize the water and maintain a flat profile. Thoughtful design makes filling, cleaning, andmost importantlystaying hydrated on the trail easier than ever.