6" DuraVent DVL Double-Wall Vermont Casting Oval To 8" Round Adaptor 8DVL-ORAD This Vermont Casting oval to 6" round adaptor is used on Vermont Casting appliances with oval flue collars to adapt to round pipe. 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.