Mid-West Canvas MW2040HVY 20 x 40 Ft. Heavy Solar Our durable 8-mil above-ground pool solar blankets can warm your pool this year by up to 15&#176;F. Thermal bubbles retain heat at night and on cool cloudy days. Our transparent blue color allows the maximum amount of solar rays to reach you pool for optimal heating. All of our blankets are U.V.-protected so they last under the most intense sunlight. 20 x 40 ft. Heavy Solar Cover Blue &#47; Clear Rectangle