The Hitech 85mm Red No. 25 Resin Filter is ideal for strong contrast improvement since it absorbs green and blue completely and enhances red. Clouds are dramatically improved almost to the mood of a thunderstorm. It is more effective in cutting through haze and moonlight effects are easily accomplished. It is also suited for infrared photography. This filter measures 85 x 85mm and fits the Cokin P series holder and the Hitech "P" series holder. The Filter factor is 4 (+2 stops).