20"w X 20"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Brown [Outer Dimensions 21.75"w x 21.75"h] Grille + Product Details Size –

+ Product Details Size – 18" x 26" or 26" x 18" is the size for the duct opening measurement only

Measure the size of the vent opening

+ Product Details Size - 36"w X 8"h is the size for the duct opening measurement only

+ Product Details Size - 12" X 12" is the size for the duct opening measurement only

+ Product Details Size – 14"w X 32"h is the size for the duct opening measurement only

20"w X 20"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Brown [Outer Dimensions 21.75"w x 21.75"h] Grille + Product Details Size –+ Product Details Size 20"w X 20"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 21. 75" Width X 21. 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