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

+ Product Details Size – 12"w X 4"h is the size for the duct opening measurement only

16"w X 3"h Is The Size For The Duct Opening Measurement Only

+ Product Details Size – 24" x 24" with 10" collar T-Bar drop ceiling perforated return grill - metal back casing

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