Just place the Small Gizzmo into your skimmers to absorb any expansion caused by freezing water. The freezing water will actually compress the Skimmer Guard instead of expanding outward and cracking your skimmer. The bottom of the Small Gizzmo fits a 1-1/2"  internal thread !
This is the Small GIZZMO. It is designed to absorb the expansion of winter freeze-up in swimming pool skimmers. The Small GIZZMO is 8 inches long and installs in short small skimmers of most in-ground swimming pools. The Small GIZZMO has 1 1/2 inch threads and features a generous bar style handle. The GIZZMO is designed for single season use. Please remember to recycle this product.
How the Gizzmo Works:  Every pool has a skimmer. When water freezes it expands. The expansion breaks the skimmer. The Gizzmo absorbs the expansion. The water crushes the gizzmo instead of destroying the skimmer. It's That Simple!  The Gizzmo is designed to absorb the expansion of winter freeze-up in skimmers only. Winterize lines and pool as per manufacturer or dealer instructions.There are many ways to winterize a pool. Consult your local pool service technician or this web site about which method you should use.