The DirectVent Pro 4 x 6-5 8 Inner Diameter Galvanized 8-1 2 Pipe Extension is a component that is used in a typical venting installation. The DuraVent pipe extension is used to add length to a straight length of DirectVent Pro. 8 ½ pipe adds 3- 7 of length, 16 pipe adds 3- 14 ½ of length, whenused with rigid sections of pipe. Direct vent lengths feature a fully unitized, twist-lock construction. Use of sealant is optional, unless specified by the appliance manufacturer. Available in black or galvalume exterior (both feature laser-welded outer wall seams). Does not fit DirectVent GS pipe.Finish: Galvanized Fuel Type: Gas, Liquid Propane Height: 8-1 2 Material: Aluminum, Galvanized Steel Pipe Class: Direct Vent Pipe Inside Diameter: 4 x 6-5 8 Pipe Shape: Round Style: Contemporary Modern UL Listed: Yes Vent Construction: Double Wall Weight: 8