36"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 37.75"w x 9.75"h] 14" Diameter Ideal for Walls & Ceilings:

Ideal for Walls & Ceilings: Designed for seamless installation in standard duct openings

For example

+ Product Details Size – 22"w X 25"h is the size for the duct opening measurement only

The total outer size of this grille is the listed size plus 1

36"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 37.75"w x 9.75"h] 14" Diameter Ideal for Walls & Ceilings:+ Product Details Size 36"w X 8"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 37. 75" Width X 9. 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