8-year 12 x 24 foot oval pool winter cover for above ground pools in the swim the swimline 12 x 24 foot heavy duty oval above ground winter swimming pool cover is great for keeping your pool in good condition during the cold, winter months, but it will also make getting your pool back into shape in the spring much easier by keeping debris out of your pool. this pool cover is made of laminated polyethylene sheeting woven with thick, high-density polyethylene stitching, which ensures superior tensile strength and durability. it has also been treated to provide maximum resistance to damaging ultraviolet rays. for the long life of your pool, choose the swimline 12 x 24 foot heavy duty oval above ground winter swimming pool cover.