12" X 4" [Duct Opening] 1-Way Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 13.75"W X 5.75"H] Fixed Blades with Damper + Product Details Size -

+ Product Details Size - 20"w X 12"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 18" x 24" OR 24" x 18" duct opening (measured at the opening)

+ Product Details Size - 4"w X 16"h is the size for the duct opening measurement only

Design – Individually adjusting curved blades

12" X 4" [Duct Opening] 1-Way Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 13.75"W X 5.75"H] Fixed Blades with Damper + Product Details Size -+ Product Details Size 12"w X 4"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 13. 75" width X 5. 75" height. High Quality High quality steel with counter sunk screw holes (screws included) and no sharp edges. Equipped with a lever for easy airflow adjustment and dampening. Airflow Control Adjustable airflow lever allows precise control over the direction and volume of air. Installation