33 x18 Round Triple-laminated poly treated against destructive UV rays for long-lasting durability. Features a plastic coated cable that you weave inbetween the alumiunum grommets every three to four feet and tighten with ratchet kit provided. Navy blue or green top with black bottom is light restrictive to resist algae and bacterial growth. Covers are 3 larger than pool to come over the top of the pool and slightly down on the outside of the pool. Suggested pillow size 4 x15 and a Stainless Steel Winter plate is recomended. Eight year limited warranty.