This 4 Inch x 6 Inch Pellet Chimney Straight Stainless Steel Length Pipe from the PelletVent Pro series is a Type L Biofuel Chimney Pipe component and consists of the duralock system for a tight seal. Features fully unitized, twist-lock construction in 3" and 4" diameters. Listed at 1" clearance to combustibles in the USA and Canada. It can be used in both vertical and horizontal installations. Stainless steel welded seam inner wall, combined with a galvalume welded seam outer wall. Pipe OD is diameter plus 5/8". Galvalume or painted black outer finish. 12" length available with stainless steel outer (SS). To calculate installed length, subtract 1 1/2" from each length of pipe. Features: Type: Straight Pipe. Pipe Class: Type L. Pipe Shape: Round. Finish: Stainless Steel. Collection: PelletVent Pro. Vent Construction: Double Wall. Outer Pipe Material: Galvalume. Inner Pipe Material: 444 Stainless Steel. UL Listed. Specifications: Overall Dimensions: 6" (L). Inner Pipe Gauge: 30. Outer Pipe Gauge: 28. Pipe Inside Diameter: 4".