The Expedition Compression features our patented Autopurge system. Constructed with radio frequency-welded seams, a lightweight 200 denier urethane-coated nylon body with end caps, and 4 compression straps. The Expedition Compression is an absolute necessity for protecting expensive sleeping bags, giving users the option of reliably carrying their sleeping bag on the outside of a pack with the peace of mind that the sleeping bag will be kept safe and dry. Our Autopurge design allows air to easily be purged from the bag while compressing.