Made from a sturdy 70D Nylon waterproof fabric in the body and lid, with an eVent waterproof but air-permeable base that allows air to be pushed out of the sack. No need for a purge valve, making these lighter and simpler. The four compression straps, use hypalon roll-top non-wicking closure. These dry sacks are the epitome of durability, versatility, and compression.