The edges are breathable, the top is a soft terry cloth material, and the base is PUL lining, which wicks the water for the terry cloth to absorb. The full size is generous enough to fully cover a plush mattress and a padded cover with room to spare. So far, this has worked great for us.
Got this because my cat "used" my bed while I was away on vacation, and I don't want to spend hours cleaning my mattress again. It doesn't have that annoying "crinkle" noise most mattress toppers do, nor do I sweat quite as much as others have historically caused me to. I haven't had a chance to see how it does protecting from my cat (and hopefully I never will!), but it fits and isn't as uncomfortable as it could be.
Wish I'd stumbled onto this product a long time ago. It fits easily on my mattress and gives me peace of mind about blocking transfer in both directions. As far as sleeping on it, I don't realize it's there. No crinkle, no increased heat, no waking up wet, which used to happen when I slept on my parents' guest bed with a plastic mattress protector. The terry surface has a really nice feel, and too bad that's hidden by my bottom sheet. It hasn't yet been subjected to the waterproof test yet, but I'm very happy with it and satisfied with other reviews and so am ordering a second one.