These sheets are secured with a super-strong polyester drawstring. They stay in place, flat and wrinkle free for a smooth, comfortable "just-made" feeling. The cord lock and drawstring are laundry safe and have a replacement guarantee for the life of the sheet. Without annoying wrinkles, these sheets allow the appreciation and enjoyment of the fabric. There is no bunching, creeping and they never pop off. Never find yourself sleeping on the bare mattress again. Enjoy not having Co straighten out the sheet every morning.