I bought this in a store about six months ago. I don't have the box, so the size isn't exact, but I think I bought a size M. Since it's a set of two, you won't have trouble with washing and changing. I've used it for about 10 days total, and I washed it in a laundry net, so there might be some pilling. It doesn't feel stretched out, so you can still use it for a while. ^_^