Fabric: Water-resistant Polyester. YKK Zipper and YKK Buckle Bottom Access:There is a divider between the sleeping bag compartment (at the bottom) and the main compartment at the top.You can access the main compartment from the bottom if needed. Hydration Compartment:Separate bladder sleeve in the main compartment.Big enough or a 3 liters hydration bladder. The rain cover comes attached to the outside on a hook but there is a pocket on the bottom for it. Hip-belt adjustable length:77-145cm/30.3-57.1in. It's not typically worn at the waist, but somewhat lower, on the hips. It's often beneficial to comfort and balance to adjust belt position while hiking, so plan to occasionally use less than the full 57" as you reposition.