The DiversiTech CVENTCAP3 3-inch Concentric Vent Cap is a PVC termination accessory designed for 3-inch concentric vent systems used with high-efficiency gas furnaces, boilers, and other Category IV heating appliances. It attaches to the vent assembly to provide a properly designed termination for combustion air intake and exhaust gas discharge through a single wall or roof opening. I... https://www.partshnc.com/cventcap3-diversitech-cap-cvent-3