10"w X 28"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 11.75"w x 29.75"h] 10" Diameter + Product Details Size -

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

+ Product Details Perfect Fit & Easy Sizing - Designed for a 36" x 8" OR 8" x 36" duct opening (measured at the opening)

Actual Filter Size – 19 3/4"w x 11 3/4" x 1"

actual front end outer dimensions are approximately 38 5/8" width X 34 5/8" height

[Outer Dimensions: 16

10"w X 28"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 11.75"w x 29.75"h] 10" Diameter + Product Details Size -+ Product Details Size 10"w X 28"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 11. 75" Width X 29. 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