18"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 19.75"w x 9.75"h] 8" Diameter + Product Details Size –

+ Product Details Size – 25"w X 12"h is the size for the duct opening measurement only

or commercial environment

the actual front end outer dimensions are 6" in diameter

+ Product Details Size - 14"w X 28"h X 2"d (for duct opening measurement only)

actual front end outer dimensions are 16" width X 8" height

18"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 19.75"w x 9.75"h] 8" Diameter + Product Details Size –+ Product Details Size 18"w X 8"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 19. 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