Keep your pool clean, pristine and heated when it's not in use with the Bestway Rectangle Solar Pool Cover. The specially-designed solar pool cover creates a greenhouse effect in your pool. By floating directly on top of the water, the cover traps heat from the sun to keep the water and warmth in and the debris out. Above ground pool covers are a must-have accessory, preventing algae growth and reducing the amount of chemicals you need to use to keep your water in tip-top shape. This cover is perfect for Bestway 6.40 m x 2.74 m (21 ft. x 9 ft.) and 7.32 m x 3.66 m (24 ft. x 12 ft.) rectangular frame pools.