The Above Ground Pool Winter Cover Air Pillow is designed to go underneath your winter cover and will compress when your pool water freezes relieving your pool walls of stress caused by ice expansion during winter The Air Pillow will also allow rain water leaves and snow to concentrate in certain areas allowing for easier removal The Air Pillow is easy to use Simply inflate the Air Pillow(s) and place it in the middle of the pool and then install and secure the winter cover in place Made of 16 gauge vinyl the Air Pillow is designed to last