6" DuraVent DuraLiner 304-Alloy Stainless Steel 12" Rigid Pipe 6DLR-12 6" x 12" DuraLiner 304-Alloy Stainless Steel 12" Rigid Pipe is used to reline masonry chimney with 0/0 clearance. Factory-insulated. Built-in pre-drilled fittings for riveting joints. 304 stainless steel inner and aluminized steel outer. Diameter: 6" Length: 12" 304-Alloy Stainless Steel Built-in pre-drilled fittings for riveting joints .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.