18"w X 24"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Brown [Outer Dimensions 19.75"w x 25.75"h] 12" Round Duct Pipe + Product Details Size –

+ Product Details Size – 36"w X 18"h is the size for the duct opening measurement only

Engineered for easy installation

this flex duct decreases the pressure loss and provides a more hygienic environment

Round-neck-to-square-face construction results in 360 degree air diffusion pattern similar to a full round diffuser

Actual Filter Size – 31 3/4"w x 27 3/4" x 1"

18"w X 24"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Brown [Outer Dimensions 19.75"w x 25.75"h] 12" Round Duct Pipe + Product Details Size –+ Product Details Size 18"w X 24"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 19. 75" Width X 25. 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