6" x 36" DuraVent DuraLiner 304 Stainless Steel Round Flex Pipe 6DLR-36F 6" x 36" DuraLiner 304 Stainless Steel Round Flex Pipe is used through 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" 304 Stainless Steel Use through damper and smoke shelf area .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.