16"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 17.75"w x 9.75"h] w36h36 Actual Filter Size – 33

Actual Filter Size – 33 3/4"w x 21 3/4" x 1"

the actual front end outer dimensions are 7" in diameter

+ Product Details Perfect Fit & Easy Sizing - Designed for a 24" x 22" OR 22" x 24" duct opening (measured at the opening)

Actual Front End Outer Dimensions Are 12" Diameter

16"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 17.75"w x 9.75"h] w36h36 Actual Filter Size – 33+ Product Details Size 16"w X 8"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 17. 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