Winter plugs are a pool closing essential. Made with durable rubber, marine-grade stainless steel, they expand in your pipes to prevent moisture damage in freezing conditions. Coming in a range of full and half sizes from 00 to 16, they can be used in returns, skimmer, main drain, and even spa jets. They can be used multiple times and stay in place all winter to prevent costly repairs after the off-season! The blow through valve allows for compressed air.