8"w X 30"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 9.75"w x 31.75"h] Floor Grille Actual Filter Size – 11

Actual Filter Size – 11 3/4"w x 9 3/4" x 1"

+ Product Details Perfect Fit & Easy Sizing - Designed for a 8" x 16" or 16" x 8" duct opening (measured at the opening)

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

Universal Fit – Measures 3-7/8" wide x 3-1/2" high x 3" deep

+ Product Details Perfect Fit & Easy Sizing - Designed for a 34" x 36" OR 36" x 34" duct opening (measured at the opening)

8"w X 30"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 9.75"w x 31.75"h] Floor Grille Actual Filter Size – 11+ Product Details Size 8"w X 30"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 9. 75" Width X 31. 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