The 801 series is a round butterfly air damper with installation ring. This butterfly damper is used to cover duct openings in conjunction with a round air diffuser. Our product is constructed to help evenly spread out airflow from your duct opening. Using our product to outfit your ventilation system will improve your home or office air circulation. Product features: Brown powder coat, high quality steel, removable knob control, and a plastic key to open/close damper.Butterfly damper controls airflow into a roomMade of high quality steelBrown powder coat finishRemovable knob control