18"w X 6"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 19.75"w x 7.75"h] 10in diameter + Product Details Perfect Fit

+ Product Details Perfect Fit & Easy Sizing - Designed for a 36" x 8" OR 8" x 36" duct opening (measured at the opening)

Actual Filter Size – 25 3/4"w x 31 3/4" x 1"

easy installation

+ Product Details Size – 28" x 30 or 30" x 28" is the size for the duct opening measurement only

18"w X 6"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 19.75"w x 7.75"h] 10in diameter + Product Details Perfect Fit+ Product Details Size 18"w X 6"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 19. 75" Width X 7. 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