18"w X 30"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 19.75"w x 31.75"h] 18" Diameter which the interior PET provides

which the interior PET provides

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Actual Filter Size – 35 3/4"w x 21 3/4" x 1"

actual front end outer dimensions are 23

18"w X 30"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 19.75"w x 31.75"h] 18" Diameter which the interior PET provides+ Product Details Size 18"w X 30"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 19. 75" Width X 31. 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