Blue Line 14-Gauge Heavy-Duty 2-ft x 2-Ft Corner Pool Water Bags for In Ground Pool Winter Covers, 4-Pack Made of 14-Gauge heavy-duty gauge, puncture resistant vinyl material Secure the corner of your winter cover with durable corner water bags, 4-Pack No leak valves Easy to fill, just use your garden hose Available in 1-pack or 4-pack