Truaire C170 10X10(Duct Opening Measurements) Return Air Grille 10-Inch by 10-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 11.75-inch in width and 11.75-inch in height.