Rugged, lightweight durability and the breathable CrossFlo suspension system give the Gregory Z55 Backpack the edge over other packs that claim to perform great in warmer climates. But, with a removable top lid and both side and bottom compression straps, the Z55 works well any time of year, for alpine climbing as well as weekend trips to the local statepark. With a recommended load capacity of 40 pounds, the Z55 is perfect for everything from overnighters to extended weekend hikes. Gregory's CrossFlo suspension system is strong, simple, and lightweight. It also provides cooling airflow across your back to pull moisture and heat away. At the heart of the system is the wire X Frame, which provides effective load transfer straight to your lumbar region and padded waist belt, where it can be carried most efficiently. The dynamic Yoke integrates the shoulder harness directly into the X Frame, activating the suspension as the weight increases to balance the frame's flexibility. The back panel is made with a moisture wicking, breathable mesh to transfer heat and moisture away from your body. To cool you even further, the hip belt and shoulder straps are made from ventilated EVA foam. Access to the Z55's main compartment is made easy with a large, U shaped zippered opening, as well as a quick draw top closure. A large zippered front pocket provides convenient storage for items that you'll need to get to through the course of your hike, such as lunch and rain gear. The pack also provides quick access to small items with dual waist belt pockets and a large dump pocket on the front of the pack. In addition, a highly water resistant top pocket with a waterproof zipper and sealed seams, in combination with an integrated rain cover, keeps your gear safe and dry when an unexpected storm pops up.