The waterproof dry bag is good for storing your dry gears when the outside is wet. It is made from heavy duty and durable PVC mesh material and produced with RWS system(Radio frequency welding seam) that electrically weld the material at molecular level into a seam that is strong and waterproof. The roll down lock with a piece of dark PE strip increase the effectiveness of the water proof seal. This is done by simply squeezing out the trapped air and folding 3 times and buckle up.