20"w X 24"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 21.75"w x 25.75"h] Ceiling Adjustable airflow control - by actual front end outer RFG1818 Black Welding & Soldering

Adjustable airflow control - by rotating the middle disk

+ Product Details Perfect Fit & Easy Sizing - Designed for a 32" x 36" Or 36" x 32" duct opening (measured at the opening)

Ideal for Walls & Ceilings: Designed for seamless installation in standard 20" X 8" duct openings

+ Product Details Size - 22"w X 18"h X 2"d (for duct opening measurement only)

+ Product Details Size - 16"w X 12"h is the size for the duct opening measurement only

20"w X 24"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace Weather Resistant Air Grille with Screen Mesh [Outer Dimensions 21.75"w x 25.75"h] Ceiling Adjustable airflow control by actual front end outer RFG1818 Black Welding & Soldering Adjustable airflow control by rotating the middle disk + Product Details Perfect Fit & Easy Sizing Designed for a 32" x 36" Or 36" x 32" duct opening (measured at the opening)