These blue solar covers are made of 12-mil, U.V. protected material. Solar covers are a fantastic way to use free heat from the sun to warm your pool water during the day and prevent heat loss at night. They work by capturing and transmitting heat directly into your swimming pool while allowing for maximum sunlight absorption. The blue color of these solar blankets absorb a greater level of heat while retaining the heat already present in your water. These solar covers are backed by a 5-year, and are available in various sizes to accommodate your pool.