Designed to keep your pool cover secure throughout the winter season when you use this Single Water Bag. Our durable, no-leak valve, and easy to use Single Tube Water Bags give you the opportunity to keep your winter pool cover secure, free of debris during harsh weather, and making pool maintenance easy. Single Tube Water Bags are great for covers with water bag loops so you don't have to worry about them rolling away. Water bags are designed to withstand sub-zero temperatures during the harsh winter weather. Simply fill the bags 1/2 to 3/4 of the way full to allow room for water expansion due to freezing. Lay them tightly on each end of your cover so that no debris can pass through. Roll each bag into the cover at least once to protect them from being popped by animals or storms.