16"w X 10"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 17.75"w x 11.75"h] 14in diameter + Product Details Size – 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size – 40"w X 10"h is the size for the duct opening measurement only

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

actual front end outer dimensions are 15

+ Product Details Size – 18"w X 10"h is the size for the duct opening measurement only

+ Product Details Size - 25"w X 32"h is the size for the duct opening measurement only

16"w X 10"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace Weather Resistant Air Grille with Screen Mesh [Outer Dimensions 17.75"w x 11.75"h] 14in diameter + Product Details Size – 4 X 12 Is CRFG2028 Width_14in + Product Details Size – 40"w X 10"h is the size for the duct opening measurement only + Product Details Size – 16"w X 16"h is the size for the duct opening measurement only