These are the floating rings that harness the power of sunlight to raise the temperature of an average-sized pool by up to 4 1/2º F per week. They require less effort to maneuver and store than traditional tarp covers, and eliminate the need for energy-consuming electrical heaters when covering just 70% of the pool's surface. Each ring acts as a partial barrier, helping to slow evaporation of water and chemicals, in addition to reducing heat loss at night. Built with an integrated spring, each ring twists and folds for storage after deflating. UV-resistant poly-vinyl. Blue. 65 1/2" L x 38" W. (1 3/4 lbs.) Set of Two