Air Pillows are a winter closing essential for aboveground pools in colder climates. This rugged vinyl air pillow absorbs the pressure of freezing and thawing to protect the cover and walls of your pool. When your pool water freezes, the Air Pillow compresses to relieve pressure on your pool walls. And by elevating your winter pool cover, Air Pillows help keep it free of leaves, debris, rainwater and snow build-up.