The Solar 8x8 Thermal Spa Blanket is a bubble-style hot tub cover designed to float comfortably on the surface of the water without ever bunching up or becoming dislodged from the use of the jets. This blanket retains heat from the sunlight when you use it underneath a traditional hard plastic spa cover. Working together, the two types of covers can help move heat from the sun directly to the surface of your spa water, which in turn keeps it heated at all times for quick use and a lower electric bill too.