6" DuraVent DuraLiner Oval Tee with Round Branch 6DLR-OTRB 6" DuraLiner Oval Tee with Round Branch provides a connection between Masonry Wall Thimble Wall Pass-Through or stove connector pipe to oval DuraLiner. Single-wall. Diameter: 6" Length: 14 1/4" Single-Wall .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.