36"w X 36"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 37.75"w x 37.75"h] Compatible with Duct 8" + Product Details Size -

+ Product Details Size - 20"w X 34"h is the size for the duct opening measurement only

Actual Filter Size – 33 3/4"w x 23 3/4" x 1"

Actual Filter Size – 29 3/4"w x 13 3/4" x 1"

+ Product Details Size – 8" x 20" or 20" x 8" is the size for the duct opening measurement only

And Meets/Beats ASTM B280 Standard

36"w X 36"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 37.75"w x 37.75"h] Compatible with Duct 8" + Product Details Size -+ Product Details Size 36"w X 36"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 37. 75" Width X 37. 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