Gas Vent Pipe; Type Type B Gas Vent, Double Wall, Round; Size 16 Inch Inner Diameter x 17 Inch Outer Diameter; Length 18 Inch; End Type Snap Lock; Material Aluminum (Inner Wall), Galvanized Steel (Outer Wall); Temperature Rating 400 Deg F; Inclusions/Features Installation Instructions are Supplied with Cap and Support; Applicable Standard UL 441The Hart & Cooley® double-wall, air-insulated B-Vent system is secured by locking joints . Properly installed, the vent won’t come apart through vibration, and offers protection against vent failure or fire hazard . Type B Gas Vent is designed for negative pressure applications and flue gas temperatures not exceeding 400°F above ambient for Category I appliances .