Thermoform technologies srb series is an industrial quality insulated duct manufactured tough for consumers' installers' peace of mind. it 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 tear resistance. A heavy duty fire retardant black polyethylene vapor barrier adds extra durability. The insulation reduces noise, heat loss condensation.