16-Year 20 x 40 ft. Rectangle Pool Winter Cover with Center Step Section and Water Tubes Features "Rip Stop" material that prevents a puncture from becoming a tear All seams are heat-sealed (not sewn) to prevent water from seeping through the cover Resistant to algae growth, mold, mildew, and common pool chemicals Heavy-duty water bag loops conveniently placed every 4 ft. to help hold water tubes firmly in place Includes qty 16 of 8ft double water tubes