When water freezes, it expands in the pipes and can cause cracks in your skimmer. With the Skimmer winter tube, water compresses the tube instead, keeping your pool protected during the winter season. Perfect for in-ground pools, the Skimmer winter tube screws in quickly into a 1-1/2" - 2" internal thread for a secure fit. Featuring a 17. 5" long cylindrical body with easy-grip top, this skimmer guard is easy to access, install, and remove.