Jamborum Backdraft Damper – 4 Inch Round – Prevent Unwanted Drafts in Metal Ducts – Professional-Grade, Heavy Duty Galvanized Steel with Aluminum Flaps – Spring-Loaded, One-Way Airflow Insert - BDD-4IN-ST-01

• Backdraft damper shutter – 4 inch – round – designed to prevent backdraft cold or warm air from flowing the wrong direction in air duct Easy installation – can be used in AC units, installation in dryer ducts, bathrooms, range hoods and heating systems, and more Heavy-duty, durable galvanized steel – strong aluminum butterfly flaps – designed to be long-lasting and functional Interior and exterior seal hold the unit in place in the air duct and prevent flaps from making loud clapping noise, spring-loaded flaps for positive closure Save energy and money by preventing backdraft – maintain the most desirable temperature, hassle-free, set it and forget it