18"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 19.75"w x 9.75"h] Compatible With Duct 6in + Product Details Perfect Fit

+ Product Details Perfect Fit & Easy Sizing - Designed for a 30" x 24" OR 24" x 30" duct opening (measured at the opening)

+ Product Details Perfect Fit & Easy Sizing - Designed for a 30" x 22" OR 22" x 30" duct opening (measured at the opening)

+ Product Details Perfect Fit & Easy Sizing - Designed for a 20" x 22" OR 22" x 20" duct opening (measured at the opening)

Actual Filter Size – 27 3/4"w x 23 3/4" x 1"

18"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 19.75"w x 9.75"h] Compatible With Duct 6in + Product Details Perfect Fit+ Product Details Size 18"w X 8"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 19. 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