Suitable Size: the bend end interface of air duct damper measures about 3.87 inches/ 9.84 cm in diameter while the other side is about 4 inches/ 10.16 cm in diameter and the height is about 6 inches/ 15.24 cm in height, which is suitable for inserting 4 inch ventilation duct Galvanized Iron Material: the 4 inch vent ducting damper is made of quality galvanized iron with high hardness and high temperature resistance, not easy to deformation and corrosion, and can effectively prevent the air duct damper from moisture and fading, which can be applied for a long time Use For Air Balance: the HVAC damper is a simple manual damper wrapped in galvanized iron sheet metal sleeves; Each branch should be fitted with an air duct damper to regulate the airflow by adjusting the position of the damper, which can help to redirect it to specific locations in the house; The 4 inch backdraft damper is not completely sealed, and it is applied for air balancing, not air termination Easy to Install: you simply slide the air ducting damper into the pipe and screw it in an easy to adjust position, then hide the seam with tape to complete the installation; It is also recommended that you can seal all connections with pipe sealant to prevent air leakage and improve the efficiency of the HVAC system Fit Most Occasions: the 4 inch HVAC damper can be applied on most occasions including air conditioning, dryer vents, exhausts, range hoods, heating systems, fans, vents and other residential, commercial and industrial HVAC applications, practical tools to use Features: Increased comfort: By controlling the airflow by a 4 inch duct damper, you can also improve the comfort level within your home or other building, which can provide a more pleasant and comfortable environment for residents, employees, or customers. Improved airflow control: The 4 inch backdraft damper helps to regulate the airflow in your system, ensuring that it is distributed evenly throughout your home or commercial building. Specifications: Material: galvanized iron Color: silver Size: about 3.87 inches/ 9.84 cm and 4 inches/ 10.16 cm in diameter, about 6 inches/ 15.24 cm in height Package includes: 2 x HVAC duct manual volume damper Notes: Manual measurement, please allow slight errors on size. The color may exist a slight difference due to different screen displays.