A Blue/Silver Thermal Cover is a great way to capture the suns heat and take full advantage of this natural resource to heat up your swimming pool! Our 11 mil thick Blue/Silver Thermal covers are made of durable resin and have thousands of tiny air bubbles designed to capture and transmit solar heat in to your pool. They will also keep your water cleaner by blocking out dirt and debris, and a Blue/Silver Thermal cover will help cut water evaporation by up to 95%, reducing heat loss at night or on cloudy days. Please remember that the bubbles on the cover face DOWN into the water!