6" - 8" DuraVent DVL Increaser 6DVL-X8 This 6" to 8" increaser is used to increase from a smaller appliance flue outlet to larger diameter chimney or stove 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.