This 4 Inch - 8 Inch Pellet Chimney Adapter from the PelletVent Pro series is a Type B gas component and consists of the duralock system for a tight seal. Use to transition between PelletVent Pro to existing chimney such as DuraTech, DuraPlus or DuraPlus HTC. Requires a DVL DuraBlack Chimney Adapter to fasten into support box or wall thimble, for 6, use adapter 8674, for 8, use adapter 8874.Finish: Stainless Steel Fuel Type: BioFuel, Oil, Pellet Height: 7 Material: Galvalume, Stainless Steel Pipe Class: Type L Pipe Inside Diameter: 4 x 8 Pipe Shape: Round Style: Contemporary Modern UL Listed: Yes Vent Construction: Double Wall Weight: 2