6"W X 16"H [Duct Opening] Steel Air Vent Return Grille - HVAC VENT DUCT COVER DIFFUSER - [Outer Dimensions: 7.75"W X 17.75"H] Material_Steel + Product Details Size – 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size – 16"w X 18"h is the size for the duct opening measurement only

positioning supply and return grills accordingly

+ Product Details Perfect Fit & Easy Sizing - Designed for a 36" x 20" OR 20" x 36" duct opening (measured at the opening)

+ Product Details Perfect Fit & Easy Sizing - Designed for a 20" x 36" OR 36" x 20" duct opening (measured at the opening)

actual front end outer dimensions are approximately 38 5/8" width X 22 5/8" height -

6"W X 16"H [Duct Opening] Steel Air Vent Return Grille HVAC VENT DUCT COVER DIFFUSER [Outer Dimensions: 7.75"W X 17.75"H] Material_Steel + Product Details Size – 4 X 12 Is CRFG2028 Width_14in + Product Details Size – 16"w X 18"h is the size for the duct opening measurement only positioning supply and return grills accordingly