12"w X 36"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace - Weather-Resistant Air Grille with Screen Mesh - [Outer Dimensions 13.75"w x 37.75"h] sidewall + Product Details Perfect Fit 4 X 12 Is CRFG2028 Width_14in

+ Product Details Perfect Fit & Easy Sizing - Designed for a 30" x 10" OR 10" x 30" duct opening (measured at the opening)

Incorporated with Integral Butterfly Damper for full Airflow Control

+ Product Details Size – 34"w X 6"h is the size for the duct opening measurement only

For 12" Round Duct Opening - Spiral or Flex

Lock and Key included

12"w X 36"h Aluminum Exterior Gable Louver Vent for Walls & Crawlspace Weather Resistant Air Grille with Screen Mesh [Outer Dimensions 13.75"w x 37.75"h] sidewall + Product Details Perfect Fit 4 X 12 Is CRFG2028 Width_14in + Product Details Perfect Fit & Easy Sizing Designed for a 30" x 10" OR 10" x 30" duct opening (measured at the opening) Incorporated with Integral Butterfly Damper for full Airflow Control