20"w X 18"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 21.75"w x 19.75"h] w24h24 + Product Details Size -

+ Product Details Size - 16"w X 36"h X 2"d (for duct opening measurement only)

+ Product Details Size – 16"w X 12"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 12" x 18" or 18" x 12" duct opening (measured at the opening)

Actual Filter Size – 29 3/4"w x 29 3/4" x 1"

20"w X 18"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 21.75"w x 19.75"h] w24h24 + Product Details Size -+ Product Details Size 20"w X 18"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 21. 75" Width X 19. 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