16"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Black [Outer Dimensions 17.75"w x 9.75"h] Grilles + Product Details Size -

+ Product Details Size - 36"w X 16"h X 2"d (for duct opening measurement only)

+ Product Details Size – 10"w X 6"h is the size for the duct opening measurement only

See chart below:

Universal Fit – Measures 6-1/4" wide x 4-3/4" high x 3" deep

+ Product Details Perfect Fit & Easy Sizing - Designed for a 20" x 26" OR 26" x 20" duct opening (measured at the opening)

16"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Black [Outer Dimensions 17.75"w x 9.75"h] Grilles + Product Details Size -+ Product Details Size 16"w X 8"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 17. 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