I've been using this mattress protector for a week after receiving it from the manufacturer to test. Although we have a pretty thick king mattress with a built-in comfort top, the protector went on easy, with room to spare. One concern I had was that it would change the way the mattress felt. After a week, I no longer have that concern. As I was putting it on, I noticed that the protectors side fabric covered the slippery smooth (yet stain-resistant and durable) fabric that covers our mattress. I thought that maybe this would prevent one of my consistent pet peeves: fitted sheets that always pop up on the corners! Well, this problem is gone, and I couldn't be happier.