"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. Outside Diameter in. 6, Material Type Fabric, Fuel Type Exhaust fans, Product Style Backdraft damper, Pieces qty. 1. Overcomes inefficiencies and limitations of other damper designs Silent operation - no noisy clanging noises Easy installation 6in. diameter"