Our Arctic Vortex deluxe series of above ground winter covers is manufactured with a tightly woven fabric that is UV treated for long life. It has a 4 foot overlap which is perfect for above ground pools with larger top rails. The black underside prevents sunlight from penetrating the cover and will stop algae growth. This cover is backed by an 8 year warranty (1 year full rated) and is navy blue with a black underside.