30"w X 16"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 31.75"w x 17.75"h] 18" Round Duct Pipe + Product Details Size -

+ Product Details Size - 16"w X 12"h X 2"d (for duct opening measurement only)

+ Product Details Size - 25"w X 20"h is the size for the duct opening measurement only

+ Product Details Size – 20"w X 40"h is the size for the duct opening measurement only

also referred to as T-Bar or Lay-in system

30"w X 16"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 31.75"w x 17.75"h] 18" Round Duct Pipe + Product Details Size -+ Product Details Size 30"w X 16"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 31. 75" Width X 17. 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