In The Swim Winter Pool Cover Air Pillow Combo Pack - 4 x 4 4 x 8 Foot Measures: 4 x 4 and 4 x 8 Feet Heavy-duty 16 gauge vinyl construction Combo pack air pillows absorb freezing water as it expands Relieves above ground pool walls from stress of ice expansion Helps reduce the build-up of rain, leaves or snow on your winter cover