DuraLiner Oval Tee with Round Branch and Cap This DuraLiner 6 Inch Chimney Relining Oval Tee and Round Branch with Cap efficiently helps venting of heating appliances while protecting masonry chimneys from the damaging effects of flue gas. Provides connection between Masonry Wall Thimble, Wall Pass Through, or stove connector pipe to oval DuraLiner. Single-wall. May require additional insulation. Refer to DuraLiner installation instructions. Features: Type: Tee with Cap. Round Branch. Tee Shape: Oval. Single Wall Construction. Provides Connection between Masonry Wall Thimble. UL Listed. Specifications: Overall Dimensions: 6″ (L). Inner Diameter: 6″.