Blue Line Heavy-Duty Air Pillows for Above Ground Pools Reduces stress from access rain, snow, ice, and leaves on your winter cover Help prolong the life of your pool and winter cover by using an air pillow Use the smaller air pillows with a round above ground pool and the larger air pillow with an oval above ground pool Equalizes the pressure created by expanding ice instead of your pool walls Available in three sizes 4-foot by 4-foot, 4-foot by 8-foot, or 4.6-foot by 15-foot