Made for 10" x 4" Duct Opening - Actual Dimensions are 11 3/4-inch x 5 3/4-inch Adjustable Flow Cntrol of Air Flow and Direction for Both Heat and AC Easy Installation with Countersunk Holes and Screws for a Flush Look Size Measurement is for Duct Opening Not Product Dimensions Solid Heavy Duty Metal Air Vent for Ceiling or Sidewall Hartford Ventilation Two Way Wall Vent Cover is and adjustable air vent cover for walls and ceilings. The multi-louver damper allows adjustment of both air flow and direction. To know correct size of wall vent, measure duct opening and select correct size.