Waterproof Design: The SleepSafe Ultra is made with 100% polyester fabric that is waterproof for protection against leaks and spills. Zipper Closure: The full box spring cover has a zipper closure for easy on and off. Durable Construction: The SleepSafe Ultra is built with a durable polyester material that is designed to last. Full Size: This waterproof box spring protector fits a standard full size mattress. Machine Washable: The SleepSafe Ultra can be conveniently cleaned by machine washing.