20"w X 20"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Black [Outer Dimensions 21.75"w x 21.75"h] w10h10 + Product Details Size –

+ Product Details Size – 12" x 30" or 30" x 12" is the size for the duct opening measurement only

3 * insulation density is 30kgs/cbm = 0

Strong aluminum frame & cube core that never rusts

Adjustable airflow control – Adjustable airflow control: The system allows users to customize the amount of air supply

+ Product Details Perfect Fit & Easy Sizing - Designed for a 18" x 20" OR 20" x 18" duct opening (measured at the opening)

20"w X 20"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - Black [Outer Dimensions 21.75"w x 21.75"h] w10h10 + Product Details Size –+ Product Details Size 20"w X 20"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 21. 75" Width X 21. 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