I thought it was a zip sealed one that goes completely around the mattress. I dont see how its is water proof neither. Its more like one for a crib mattress. Only the top is covered and protected. The sides are mesh. Its alright. It does make a slight crunchy noise but I put a comforter over my sheets and then another one of top of that one so I dont hear it. Probably wont buy this one again. Its cheap so you get what u pay for