18"w X 18"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Black [Outer Dimensions 19.75"w x 19.75"h] 18" Round Duct Pipe + Product Details Size -

+ Product Details Size - 18"w X 34"h is the size for the duct opening measurement only

+ Product Details Size – 20" x 26 or 26" x 20" is the size for the duct opening measurement only

See our separate listing of T-Bar Supply Grilles

+ Product Details Size - 6"w X 30"h X 2"d (for duct opening measurement only)

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