Truaire C165-RMB 04X12(Duct Opening Measurements) Decorative Floor Grille 4-Inch by 12-Inch Retro Couture Floor Diffuser, Matte Black Finish Smoothglide damper Model Size Indicates Duct Opening Measurements not Wall Opening Measurements. High quality steel components , no plastic High quality plating The actual face size is 13.5-inch in width and 5.5-inch in height.