18"w X 20"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 19.75"w x 21.75"h] w26h26 Actual Filter Size – 24

Actual Filter Size – 24 3/4"w x 25 3/4" x 1"

Actual Filter Size – 35 3/4"w x 33 3/4" x 1"

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

+ Product Details Size - 36"w X 22"h is the size for the duct opening measurement only

18"w X 20"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 19.75"w x 21.75"h] w26h26 Actual Filter Size – 24+ Product Details Size 18"w X 20"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 19. 75" Width X 21. 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