6" x 36" DuraVent DuraLiner Stainless Steel Oval Flex Pipe 6DLR-36OF 6" x 36" DuraLiner Stainless Steel Oval Flex Pipe is used through the damper and smoke shelf area. Use with DuraLiner Insulation Kit (ProMesh and ProFoil) where flex extends into clay liner for zero-clearance applications. Built from 1-plyconstruction .005" 304 stainless steel. Diameter: 6" Length: 36" Stainless Steel .016” 304 stainless steel inner liner. Rigid relining pipe: double-walled with 304 stainless steel inner and galvalume outer. Factory insulated between inner and outer walls.