Lightweight durability and a breathable suspension system give the Gregory Z 55 Backpack the edge over other packs that claim to perform great in warmer climates. But, with a removable top lid and multiple compression options, the Z 55 works well any time of year, for alpine climbing as well as weekend trips to the local state park. With a maximum load recommendation of 40 pounds, the Z 55 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. Access to the Z 55's main compartment is made easy with a large, u shaped zippered opening. 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 easy access to small items with dual waist belt pockets and a large dump pocket on the front of the pack, as well as a highly water resistant top pocket with a waterproof zipper and sealed seams. And, speaking of waterproof, the Z 55 comes with an integrated, color matched rain cover to keep your gear safe and dry when an unexpected storm pops up.