Topeak uses air for comfort and support in their lightweight Air BackPack. A tiny hand pump inflates the back and sides of the pack allowing you to customize the amount of supporting air pressure. Depending on the weight and size of your load, you can dial in a perfect fit allowing you to concentrate on your ride and not the gear on your back. Some of the nice features of the Air Back Pack include a hydration bladder compartment, helmet holder and rainfly. And, when not in use, the Air BackPack collapses down into a stuff sack for excellent portability.