20"w X 6"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 21.75"w x 7.75"h] Compatible With Duct 12in + Product Details Perfect Fit

+ Product Details Perfect Fit & Easy Sizing - Designed for a 24" x 12" OR 12" x 24" duct opening (measured at the opening)

+ Product Details Size - 30"w X 26"h is the size for the duct opening measurement only

Actual Filter Size – 21 3/4"w x 35 3/4" x 1"

actual front end outer dimensions are approximately 16 5/8" width X 27 5/8" height

20"w X 6"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 21.75"w x 7.75"h] Compatible With Duct 12in + Product Details Perfect Fit+ Product Details Size 20"w X 6"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 21. 75" Width X 7. 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