The 9" Swimline Hydrotools Skimmer guard will fit almost all skimmers and protects your skimmer from damage caused by ice when the pool water freezes and expands. The 9" Skimmer Guard is recommended for use in skimmers that have a limited height. This expanding ice will push against the sides of your skimmer and cause it to crack. With the Skimmer Guard in place, the ice will be able to push in on the Skimmer Guard and prevent damage to your pool skimmer saving you time and money in the spring. The Skimmer Guard is designed to fit both 1 1/2" and 2" internal (female) skimmer threads.