ThermoFlo™ SRB Series Ducting is an industrial-quality insulated flexible air duct manufactured tough for consumer and installer peace of mind. It features high-standard c-ETL-us / Can / ULC-S110-M86 / UL 181 approved cores. The SRB Series ducting consists of a three-ply polyester laminate, fiberglass reinforced scrim, and galvanized spring steel wire wrapped with fiberglass insulation which provides an outstanding combination of strength and tear resistance. The insulation reduces heat loss and condensation while a heavy-duty fire-retardant black polyethylene vapor barrier adds extra durability. Made in Canada, this 25-foot (7.6-meter) ducting is available in a variety of sizes and custom lengths can be special ordered. The ducting is marked approximately every foot and is easy to install with instructions included in each case.