6"w X 18"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 7.75"w x 19.75"h] Compatible with Duct 8" + Product Details Size -

+ Product Details Size - 30"w X 25"h is the size for the duct opening measurement only

fasten the edges to studs with the provided screws

our damper is designed to perfectly align with your setup

you can attain the diameter of the vent

6"w X 18"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 7.75"w x 19.75"h] Compatible with Duct 8" + Product Details Size -+ Product Details Size 6"w X 18"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 7. 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 wear