"This Tamarack Backdraft Damper uses a specially formulated fabric sleeve attached to an outer metal sleeve to allow maximum airflow while stopping cold air from entering your home. U.S.A. Material Type Fabric, Outside Diameter in. 6, Pieces qty. 1, Product Style Backdraft damper, Fuel Type Exhaust fans. Overcomes inefficiencies and limitations of other damper designs Silent operation - no noisy clanging noises Easy installation 6in. diameter"