This ProMaster HGX Prime VND filter mounts to lenses with 67mm threads and provides an exposure reduction of 1.3 to 8 stops (ND2.5-ND256 equivalent). It darkens the entire image allowing for slower shutter speeds and/or wider apertures with applications for both still photography and videography.Mechanical “hard” stops at each end of the filter’s range prevent bypassing the minimum or maximum useable density. A small, knurled knob provides a tactile experience making it easier to rotate the filter quickly and smoothly, simply by touch. This Tactile Control Knob is removable if you prefer not to use it.White lines on the filter’s ring indicate its density setting at each full stop. These lines represent specific densities of 2, 3, 4, 5, 6, and 7 stops with 1.3 and 8 stops being achieved at each end of the filter ring’s range of travel (MIN and MAX positions).An additional “X” mark on the filter’s ring indicates the density point at which cross polarization (X pattern) begins, slightly, to visually appear when using most wide-angle lenses (a phenomenon common to all VND filters).