We have a king Tempur-Pedic "cooling" mattress that will not hold a sheet. We have tried sheets with corner straps and that was a waste of money, to say the least. I was so tired of the sheet being all wrinkled under me in the morning, so I finally purchased two sets of these bed sheet suspenders. They actually work! The elastic is adjustable and the clips hold fast to the edge of the sheet without damaging it. Like I said, I did buy two sets, so two go up/down the bed, and two side to side. Maybe a little overkill, but well worth the price of no wrinkly sheets or popped off corners in the morning.