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