8" X 6" [Duct Opening] 3-Way Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 9.75"H X 7.75"H] 18" Round Duct Pipe The first number in a

The first number in a grille size

Actual Filter Size – 31 3/4"w x 23 3/4" x 1"

these heavy-duty louvers are ideal for use in attics

[Outer Dimensions: 26

8" X 6" [Duct Opening] 3-Way Fixed Curved Blade Air Supply Diffuser Register Vent Cover Grille [Outer Dimensions: 9.75"H X 7.75"H] 18" Round Duct Pipe The first number in a+ Product Details Size 8"w X 6"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 9. 75" width X 7. 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