Hitech 85mm Neutral Density (ND) 0.9 Resin Filter reduces the amount of light reaching the film. It has no effects on color balance. It has four main uses: 1) To enable slow shutter speeds to be used, especially with high speed films, to record movement in subjects such as waterfalls, clouds, or cars. 2) To decrease depth of field by allowing wider apertures to be used, which helps separate subjects from their background. 3) To decrease the effective ISO of high speed film (above ISO 400) and allow it to be used outdoors in bright situations. 4) To allow cine and video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes which could cause overexposure. This filter measures 85 x 85mm and fits the Cokin P series holder and the Hitech "P" series holder.