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" you can attain the diameter

you can attain the diameter of the vent

but you will appreciate the benefits over the period of time

The integral design allows you to easily adjust the curved blades

+ Product Details Size – 10"w X 18"h is the size for the duct opening measurement only

+ Product Details Size – 18"w X 16"h is the size for the duct opening measurement only

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" you can attain the diameter+ 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