The Olympus pool cover is an advanced, premium 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. Please order a larger size cover if you have steps protruding from your pool. This cover includes a 5 ft. overlap. While this cover is lighter and easier to handle than standard pool covers, it is twice as strong. The Olympus Pool Cover features interlocking dual-layers of high-density, premium polyethylene. The Olympus has a premium 13 x 11 scrim. Heavy-duty premium polyethylene weighs 3.6 oz./yd2. Tear-resistant RipShield technology prevents punctures from expanding into significant tears. The blue 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. Premium water bag loops (water bags sold separately) are placed every 4 ft. and premium grommets are sewn into the water bag loops and at each corner. Water bags or water tubes are the only recommended method of installation.The cover should be able to comfortably float on the pool water without excessive stress. Includes a 20-years warranty.