18"w X 24"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - White [Outer Dimensions 19.75"w x 25.75"h] 10" Round Duct Pipe + Product Details Size – 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size – 10" x 26" or 26" x 10" is the size for the duct opening measurement only

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+ Product Details Size - 18"w X 34"h is the size for the duct opening measurement only

+ Product Details Size - 12"w X 12"h X 2"d (for duct opening measurement only)

+ Product Details Perfect Fit & Easy Sizing - Designed for a 34" x 8" Or 8" x 34" duct opening (measured at the opening)

18"w X 24"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace Weather Resistant Air Grille with Screen Mesh White [Outer Dimensions 19.75"w x 25.75"h] 10" Round Duct Pipe + Product Details Size – 4 X 12 Is CRFG2028 Width_14in + Product Details Size – 10" x 26" or 26" x 10" is the size for the duct opening measurement only margin right: 8px