12"w X 6"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 13.75"w x 7.75"h] White + Product Details Size –

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

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

This versatile diffuser is adaptable to various airflow needs

actual front end outer dimensions are approximately 27 5/8" width X 22 5/8" height

+ Product Details Perfect Fit & Easy Sizing - Designed for a 8" x 30" or 30" x 8" duct opening (measured at the opening)

12"w X 6"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 13.75"w x 7.75"h] White + Product Details Size –+ Product Details Size 12"w X 6"h X 2"d (for duct opening measurement only); actual front end outer dimensions are 13. 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