4x4" Resin Standard Neutral Density ND2 ND4 ND8 100ND 100mm ND Filter Kit Size: 4" x 4" (100mm x 100mm) Ideal for reducing bright light in large aperture situations when a narrow depth is field is needed. Allows for slower shutter speeds when blurring or showing of movement is desired. Allows balancing of exposure to highlight a key subject. Lets you use higher speed films in bright light.