32"w X 12"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 33.75"w x 13.75"h] 18in diameter + Product Details Size -

+ Product Details Size - 20"w X 30"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 30 5/8" width X 20 5/8" height

For 12" Round Duct Opening - Spiral or Flex

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

+ Product Details Size - 25"w X 22"h is the size for the duct opening measurement only

32"w X 12"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 33.75"w x 13.75"h] 18in diameter + Product Details Size -+ Product Details Size 32"w X 12"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 33. 75" Width X 13. 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