16"w X 20"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 17.75"w x 21.75"h] Ceiling making it a reliable choice

making it a reliable choice for improving indoor air quality

+ Product Details Size - 18"w X 20"h is the size for the duct opening measurement only

+ Product Details Size - 28"w X 20"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 10" x 18" or 18" x 10" duct opening (measured at the opening)

Actual Filter Size – 33 3/4"w x 15 3/4" x 1"

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