Truaire C154R 10X10(Duct Opening Measurements) Heavy Duty Floor Return Air Grille 10-Inch by 10-Inch Floor Return Air Grille, Brown Extremely ridged construction Model Size Indicates Duct Opening Measurements not Wall Opening Measurements. Over 75% free area High quality powder coated The actual face size is 11.8-inch in width and 11.8-inch in height.