These Blue 10' Winter Water Tube Bags help to keep everything securely in place. They are constructed of heavy-duty 16-gauge, puncture-resistant material. All of these double-chamber water bags for in-ground swimming pool covers have a conveniently placed, leak-proof valve. They are easy to fill with a garden hose and the design keeps them from rolling. These vinyl water tubes should be filled half-way to prevent popping caused by expansion if there is any freezing. This item is available in a choice of assorted size packs.