6"w X 24"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 7.75"w x 25.75"h] 6" Round Duct Pipe + Product Details Size –

+ Product Details Size – 8"w X 18"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 18" x 8" OR 8" X 18" duct opening (measured at the opening)

+ Product Details Size – 18" x 20" or 20" x 18" is the size for the duct opening measurement only

actual front end outer dimensions are approximately 16 5/8" width X 38 5/8" height

6"w X 24"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 7.75"w x 25.75"h] 6" Round Duct Pipe + Product Details Size –+ Product Details Size 6"w X 24"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 7. 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 wear