4" x 12" PelletVent Pro Double-Wall Black Pipe Length 4PVP-12B This chimney pipe features fully unitized twist-lock construction. 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. To calculate installed length subtract 1 1⁄2” from each length of pipe. Use with pellet oil corn and bio-fuel appliances Laser-welded super ferritic stainless steel inner walls and galvalume outer walls Outer diameter is 5/8" larger than inner diameter 1" clearance to combustibles No additional gaskets or sealants needed The precise fit of twist-lock connections is fast secure and leak resistant. Adaptability is provided by swivel elbow connections and multiple termination options Laser-welded double-wall pipe with a .012” inner wall of corrosion resistant stainless steel and a .018” laser-welded galvalume outer wall. Painted black exterior available. Primary metal-to-metal connection seals joint. Encapsulated O-ring provides a secondary seal.