The Osprey Osprey Packs Ultralight Dry Sack is waterproof gear storage for your sleeping bag, clothing, and whatever else you need to keep dry on the trail. The 40D nylon ripstop fabric is durable, yet ultralight, with waterproof coating throughout as well as coated seams. The roll-top closure secures it closed with a clip. Conveniently shaped like a rectangle so you can align your backpack Tetris-style. Designed to keep your gear bone dry, Osprey’s Dry Sacks provide the security of waterproof gear storage and color coded organization in your pack.