I bought this mattress cover for our bed after my husband had just had an ileostomy. It doesn't have a nap surface, which I couldn't tell from the product information when buying it. Consequently I found that our own sheet slides on it and this being fitted, I found that the corners sometimes slide out of position overnight and you find yourself shipwrecked and sweaty on the plastic, alongside waves of rumpled bottom sheet. I normally sleep like a log so I don't think fidgeting is the cause.
This wouldn't happen I feel if it had a nap (or furry) surface. I can't wait to get it off the bed.
In fairness to the manufacturers our matress is fairly deep, but our cotton bottom sheets normally stay put.