We bought two of these for our swan, they are waterproof, terry top, fitted mattress protectors. Our little girl wears undies to bed (she's only 3) and although she never wets the bed I didn't want to jinx it by not putting protectors on. Luckily enough she never has had an accident but it's good to know our mattresses are protected no matter what. We always pack up with our bed end flies still up and it's rained nearly every time we have been camping, our canvas stays dry underneath and we have never had water on the beds or the canvas. We have to air our the bed flies and awnings when we get home, but the actual camper canvas stays pretty much completely dry when your covered all around with awnings and bed flies.