This ThermoFlo Insulated Ducting is an industrial quality insulated duct manufactured tough for consumers and installers peace of mind. It features the high standard c-ETL-us - Can - ULC-S110-M86 - UL 181 approved cores from ThermoFlo. The SRB series duct consists of a three ply polyester laminate, fiberglass reinforced scrim, galvanized spring steel wire, wrapped with fiberglass insulation, which provides an outstanding combination of strength and tear resistance. A heavy duty fire retardant black polyethylene vapor barrier adds extra durability. Marked approximately every foot and is easy to install.