26"w X 6"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 27.75"w x 7.75"h] Aluminum Bar + Product Details Size -

+ Product Details Size - 18"w X 10"h is the size for the duct opening measurement only

it integrates effortlessly into T-bar or plaster frame ceilings

+ Product Details Size – 18"w X 12"h is the size for the duct opening measurement only

+ Product Details Size - 26"w X 20"h is the size for the duct opening measurement only

Actual Front End Outer Dimensions Are 8" Diameter

26"w X 6"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 27.75"w x 7.75"h] Aluminum Bar + Product Details Size -+ Product Details Size 26"w X 6"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 27. 75" Width X 7. 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