Durable 8 foot water bags made with 20 gauge vinyl. These water bags are made with high quality, high performance and come equipped with no leak valves so they will last more than one closing season. It is recommended that these water bags be filled about 1/2 to 3/4 full. To prevent the water from freezing in the bags over the cold winter months, simply add some pool or RV antifreeze in the bag. The double chamber adds for extra weight and protection so they won't roll or slide off onto the ground our onto the pool cover.