The Hoya Variable Density II filter provides a convenient way to maintain exposure control by being able to vary the amount of light entering the camera by 1.5 to 9 stops (ND3-ND400). The precision built-in double ring design with special knob allows the outer ring rotates to control amount of neutral density effect anywhere within the 1.5 – 9 stop range. Hoya Variable Density II replaces a whole set of neutral density filters from ND3 to ND400.