This 3 Inch - 4 Inch Pellet Chimney Increaser from the PelletVent Pro series is a Type B gas component and consists of the duralock system for a tight seal. Use to transition from 3 pipe to a 4 pipe. Not a decreaser or stove adapter.Finish: Stainless Steel Fuel Type: BioFuel, Oil, Pellet Height: 4-3 4 Material: Galvalume, Stainless Steel Pipe Class: Type L Pipe Inside Diameter: 3, 4 Pipe Shape: Round Style: Contemporary Modern UL Listed: Yes Vent Construction: Double Wall Weight: 1