36"w X 26"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 37.75"w x 27.75"h] 12" Round Duct Pipe Actual Filter Size – 27

Actual Filter Size – 27 3/4"w x 27 3/4" x 1"

+ Product Details Size - 18"w X 36"h is the size for the duct opening measurement only

Incorporated with Integral Butterfly Damper for full Airflow Control

Actual Filter Size – 21 3/4"w x 15 3/4" x 1"

36"w X 26"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 37.75"w x 27.75"h] 12" Round Duct Pipe Actual Filter Size – 27+ Product Details Size 36"w X 26"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 37. 75" Width X 27. 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