This 4 Inch x 12 Inch Pellet Chimney Black Pipe Extension from the PelletVent Pro series is a Type B gas component and consists of the duralock system for a tight seal. Use to add length to PelletVent Pro pipe. 12 pipe adds 3-10 of length, 18 pipe adds 3-16 of length, when used with rigid sections of pipe. Galvalume or painted black outer finish.Finish: Black Fuel Type: BioFuel, Oil, Pellet Length: 3 - 10 Material: Galvalume, Stainless Steel Pipe Class: Type L Pipe Inside Diameter: 4 Pipe Shape: Round Style: Contemporary Modern UL Listed: Yes Vent Construction: Double Wall Weight: 2