8" DuraVent DVL Double-Wall Black Tee with Clean-Out Cap 8DVL-T This tee with clean-out cap is used to create a solid connection with rear exit appliances and appliances that require a barometric damper. The clean-out cap makes cleaning and maintenance much easier. Use with DuraVent factory-built chimneys 430-alloy stainless inner wall aluminized steel outer wall 1" outer diameter Reduces clearances from 18" to 6" for walls Reduces clearances from 18" to 8" for ceilings Sturdy construction to ensure long-lasting durability Creates a tight secure connection in your venting system .016” stainless steel inner wall. .018” galvanized outer painted black.