Plastic furnace or AC vent with damper. Damper can be easily opened and closed for control of air flow. 1 per pack. BRD Rotaire Register. Rotaire register is molded from durable ABS plastic. The damper mechanism can easily be opened and closed and may be completely removed for full flow. Grill rotates a full 360 degrees to direct air flow where desired. 4 Inch Diameter mounting collar; overall 5 Inch Diameter by 2.75 Inch Depth White 4 Inch. BRD Rotaire Register. Rotaire register is molded from durable ABS plastic. The damper mechanism can easily be opened and closed and may be completely removed for full flow. Grill rotates a full 360 degrees to direct air flow where desired. 4 Inch Diameter mounting collar; overall 5 Inch Diameter by 2.75 Inch Depth White 4 Inch.