20"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 21.75"w x 9.75"h] Floor Grille + Product Details Size - 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size - 18"w X 24"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 32 5/8" width X 8 5/8" height

+ Product Details Size – 14"w X 30"h is the size for the duct opening measurement only

+ Product Details Size - 14"w X 8"h X 2"d (for duct opening measurement only)

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20"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace Weather Resistant Air Grille with Screen Mesh [Outer Dimensions 21.75"w x 9.75"h] Floor Grille + Product Details Size 4 X 12 Is CRFG2028 Width_14in + Product Details Size 18"w X 24"h is the size for the duct opening measurement only actual front end outer dimensions are approximately 32 5 8" width X 8 5 8" height