20"w X 16"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 21.75"w x 17.75"h] Grilles 2 recessed screw holes on

2 recessed screw holes on each side with screws included

+ Product Description Introducing the 6" Butterfly Damper – Your Solution for Controlled Airflow

+ Product Details Size – 16" x 28" or 28" x 16" is the size for the duct opening measurement only

+ Product Details Size - 25"w X 22"h is the size for the duct opening measurement only

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