In The Swim 16 Mil Ultra Clear Swimming Pool Solar Blanket Cover 21 ft. Round 16-mil thick solar blanket constructed from UV-stabilized resin Thousands of tiny air bubbles work to transfer solar heat into your pool Reduces chemical loss through evaporation, saving time and money on chemicals and rebalancing Can be easily cut or trimmed to fit kidney, oval or irregularly shaped pools Backed by an 8-Year Limited Manufacturer's Warranty