The Pool Mate Deluxe Winterizing Air Pillow absorbs stress created by ice building up in your pool. As ice expands in your pool the pressure created is exerted onto the pillow instead of the walls of your pool. Ice equalizer pillows are an essential way to protect your pool during the winter. The pillow will pop before the ice damages your pool. Ice Equalizer pillows also reduce the build-up of rain water, leaves and snow on your winter cover. All you have to do is inflate the pillow and place it under your cover during the winter months. Do not overfill the pillow with air, as this can cause the valve to pop out during the winter months (1/2 to 3/4 full is recommended). Smaller equalizer pillows are recommended for round pools and larger equalizer pillows are recommended for oval pools. Using additional pillows will protect your pool if one fails. Using additional pillows may require a larger than expected pool cover size. 4-Pack Classic 4 ft. x 5 ft. Pool Pillow for Winterizing Above Ground Pools Classic .22 MM Thick Vinyl constructed 37% heavier than industry standard. Since 1999 Pool Mate has been making the best products to close your pool. Use the best pool closing products designed with over 25 years of experience. Absorbs Pressure Caused By Ice Build Up Under Pool Cover Preventing Damage To Pool Walls. Pool Pillow Will Pop Before Ice Damages Pool Walls. Forces Debris From The Center Of The Pool To The Sides For Easier Cleaning Lifts Pool Cover To Prevent Water From Leeching Through Pool Cover Fill Halfway to Two-Thirds With Air to Prevent Premature Popping. If you have trouble closing the valve please use a hair dryer to loosen before closing. UPC 034261925550 ASIN B010K6LHFU Color Blue Shape Rectangular Brand Name Pool Mate Unit Count 4.0 Count Item Weight 7 Pounds Manufacturer Pool Mate Model Number 1-3745--04 Material Type Vinyl Required Assembly No Included Components Pool Pillow x4 Indoor Outdoor Usage Outdoor Manufacturer Part Number 1-3745--04 Item Dimensions L x W x H 48 L x 48 W x 60 H Global Trade Identification Number 00034261925550 Other Special Features of the Product Above Ground