Our expanding rubber plugs will help you with keeping water out of your lines and your equipment safe from breaking from freezing/expanding water after the water has been drained from your pool or blown from your lines. Our rubber plugs can be used on your pool or spas plumbing lines, inlets, outlets and skimmers. Our rubber plugs diameter will expand up to 0.25 of an inch by turning the nylon wing nut attached. 5 sizes available to choose from to find your perfect fit for over the winter.