The Swimline 10 Foot Double Water Tube is made specifically for use with your rectangular or oval pool cover to eliminate stress on your pool and the cover. It's 33% heavier then other water bags, making it super durable, and its valves are easy to fill up with a garden hose. This Swimline water tube is best used with in ground pool covers.Covering your pool with a winter cover keeps out dirt and debris. This water tube helps keep the cover in place.We are an Authorized Swimline Swimming Pool parts dealer! These water tubes are backed by a 1 year manufacturer warranty!