12" X 12" [Duct Opening] 2-Way Horizontal Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 13.75"W X 13.75"H] sidewall + Product Details Size -

+ Product Details Size - 4"w X 32"h is the size for the duct opening measurement only

The crank handle lever makes it easy to adjust to every weather situation

1/2" White insulation will give you a good R value of 3

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Optional Butterfly Damper Available At Asin: B007CNEL1W

12" X 12" [Duct Opening] 2-Way Horizontal Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 13.75"W X 13.75"H] sidewall + Product Details Size -+ Product Details Size 12"w X 12"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 13. 75" width X 13. 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