16"w X 20"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 17.75"w x 21.75"h] Insulated Line + Product Details Size –

+ Product Details Size – 10"w X 16"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 12 5/8" width X 28 5/8" height

+ Product Details Size – 16" x 20" or 20" x 16" is the size for the duct opening measurement only

Think of the diameter as a straight line from one end to the other

actual front end outer dimensions are approximately 10 5/8" width X 18 5/8" height

16"w X 20"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 17.75"w x 21.75"h] Insulated Line + Product Details Size –+ Product Details Size 16"w X 20"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 17. 75" Width X 21. 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