The Supreme pool cover is a extra heavy-duty solid winter cover. Solid pool covers do not allow water to pass through their material. This winter cover is intended to be used during the off-season. Please order by your pool size, as the overlap goes beyond the pool size listed. This cover includes a four-foot overlap. If you have a very large top rail, please consider a larger pool size. The Supreme winter cover features a extra heavy-duty scrim count (threads per square inch). The Supreme pool cover has a extra heavy-duty 12 x 12 scrim. Extra heavy-duty polyethylene weighs 3.26 oz./yd2. Both the scrim count and material weight are the best indicators of the overall strength and durability of your pool cover. The green topside of this cover is coated to prevent damage caused by the sun's ultra-violet rays and the bottom side is black to prevent algae growth. Two grommets are placed on center every four feet, with these grommets, you should use the included winch and all-weather cable to secure your pool cover. For extra securing, cover clips and cover wrap (both sold separately) are suggested for pool closing. No other method of installation is recommended. The cover should be able to comfortably float on the pool water without excessive stress. Includes a 12 year warranty.