10"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 11.75"w x 9.75"h] 10in diameter + Product Details Size -

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

Actual Filter Size – 7 3/4"w x 31 3/4" x 1"

+ Product Details Perfect Fit & Easy Sizing - Designed for a 28" x 18" OR 18" x 28" duct opening (measured at the opening)

Actual Filter Size – 47 3/4"w x 23 3/4" x 1"

+ Product Details Size – 22"w X 16"h is the size for the duct opening measurement only

10"w X 8"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 11.75"w x 9.75"h] 10in diameter + Product Details Size -+ Product Details Size 10"w X 8"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 11. 75" Width X 9. 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 wear