18"w X 18"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Black [Outer Dimensions 19.75"w x 19.75"h] 10" Diameter + Product Details Size –

+ Product Details Size – 12" x 30" or 30" x 12" is the size for the duct opening measurement only

1/2" White insulation will give you a good R value of 3

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

ensuring a perfect fit

+ Product Details Perfect Fit & Easy Sizing - Designed for a 16" x 32" OR 32" X 16" duct opening (measured at the opening)

18"w X 18"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Black [Outer Dimensions 19.75"w x 19.75"h] 10" Diameter + 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