Simpooltec AGWM-LH Hercules Rapid Flow Skimmer Plug WM Skimmer plug offers a simple yet revolutionary method for servicing and winterizing the rapid flow skimmer on your above ground pool Keeps skimmer dray all winter long to prevent freeze damage without draining the pool water Blocks water from entering the skimmer, making servicing your pool fast and easy Skimmer plug's rigid outer plate provides a durable and secure layer of protection through the winter Creates a 100-percent air-tight hydrostatic seal