The Weil McLain 450-021-242 Draft Diverter 5" to 6" is a precision-engineered venting component designed to regulate draft and ensure the safe discharge of combustion gases from compatible boilers and HVAC heating systems. It works by stabilizing airflow between the appliance and venting system, helping maintain proper combustion while minimizing the effects of downdrafts and excessiv... https://www.partshnc.com/5-to-6-draft-diverter