The Pool Mate Classic Above-Ground Pool Cover protects your pool during harsh winter conditions. The polyethylene material stops algae growth by preventing UV rays from entering your pool. This solid pool cover also blocks dirt and debris from getting into the water. Pool owners who use a Pool Mate Classic Pool Cover and close their pool with the proper winterizing chemicals will have a clean pool in the spring that will be easy to open. it is always recommended to open your pool by mid to late may to prevent algae growth. The cover should be able to float comfortably on the water. Please order a larger size if you have a large top rail. Grommets are placed every 4 feet and should be used with the included cable and winch. The lightweight material is more durable than regular covers because all seams are heat sealed for better performance. The Pool Mate Classic Above-Ground Pool Cover comes with an 8-year warranty.