Our heavy duty tan 8 foot, 18 gauge double water tubes are designed to hold down your in ground pool winter cover and help it stay put through the winter. Simply filling the water tubes about 1/2 way will provide the extra weight needed to help hold down your cover under the most sever weather conditions. If one side becomes punctured, there is still enough weight from the other chamber to hold your cover down - no rush to replace a water tube in cold weather