Use compressed air to clear RV water lines before winterizing to avoid diluting antifreeze. Easy to use, this blow-out plug screws into your RV's city water inlet so you can open all drains and faucets and blow air through your lines before storage. Built-in Schrader valve works with most air hoses. Durable plastic construction will provide years of use. Built-in Schrader valve works with most air hoses Durable plastic construction | Blow Out Plug, Black