PATIKIL 2 Sets 3-Inch 4-Inch 5-Inch Backdraft Damper ABS Flexible Airflow Inline Backflow Duct Adaptor Draft Blocker for Bathroom Exhaust Fan

The backdraft damper prevents lampblack, exhaust, debris, dust, and odors from entering your room when the ventilation fan is off, and is widely used in dryers, range hoods, and HVAC systems in homes, kitchens, bathrooms, and offices.

Made of durable ABS plastic, it is waterproof, hard, scratch-resistant, oil-resistant, high-temperature resistant, moisture-proof, and easy to clean for long-term use.

When exhaust starts, air pressure opens the valve for discharge; after stopping, it automatically closes to keep indoor air fresh.

Installation is simple: apply sealing glue around the base, secure with screws to the vent hole, and attach the vent hose with tape if necessary.

Please confirm the outer diameter before ordering.