8"w X 12"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 9.75"w x 13.75"h] Grilles Actual Filter Size – 31

Actual Filter Size – 31 3/4"w x 5 3/4" x 1"

+ Product Details Size – 18" x 32" or 32" x 18" is the size for the duct opening measurement only

actual front end outer dimensions are 21

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+ Product Details Size - 8"w X 34"h is the size for the duct opening measurement only

8"w X 12"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 9.75"w x 13.75"h] Grilles Actual Filter Size – 31+ Product Details Size 8"w X 12"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 9. 75" Width X 13. 75" Height Weather and Pest Proof These louvers are especially designed to prevent water from entering your home, and with a built in back 1 2" mesh they also protect you from annoying rodents like mice, rats, birds, and squirrels High Quality Aluminum The premium durable aluminum will never rust and it will never wear