8" X 4" [Duct Opening] 3-Way Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 9.75"W X 5.75"H] Powder-Coated you can attain the diameter

you can attain the diameter of the vent

actual front end outer dimensions are approximately 18 5/8" width X 26 5/8" height -

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actual front end outer dimensions are approximately 16 5/8" width X 10 5/8" height -

8" X 4" [Duct Opening] 3-Way Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 9.75"W X 5.75"H] Powder-Coated you can attain the diameter+ Product Details Size 8"w X 4"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 9. 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 Location