Truaire C170 20X20(Duct Opening Measurements) Return Air Grille 20-Inch by 20-Inch Sidewall or Ceiling Return Air Grille, White Heavy gage all steel construction Model Size Indicates Duct Opening Measurements not Wall Opening Measurements. 1/2-inch spaced fins High quality powder coated The actual face size is 21.75-inch in width and 21.75-inch in height.