10"W X 14"H [Duct Opening] Steel Air Vent Return Grille - HVAC VENT DUCT COVER DIFFUSER - [Outer Dimensions: 11.75"W X 15.75"H] w18h18 + Product Details Size - 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size - 36"w X 24"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 5

+ Product Details Size - 12"w X 16"h is the size for the duct opening measurement only

If you are looking to enhance your project with a top-of-the-line unit

+ Product Details Size - 24"w X 24"h is the size for the duct opening measurement only

10"W X 14"H [Duct Opening] Steel Air Vent Return Grille HVAC VENT DUCT COVER DIFFUSER [Outer Dimensions: 11.75"W X 15.75"H] w18h18 + Product Details Size 4 X 12 Is CRFG2028 Width_14in + Product Details Size 36"w X 24"h is the size for the duct opening measurement only actual front end outer dimensions are approximately 5