The Sirui ND64 – 6 Stop (1.8) Square Filter – 100x100mm is a Neutral density filter designed to designed darken the entire image by 6 stops, allowing you to create images with wider apertures or slower shutter speeds. By slowing your exposure time or increasing your aperture, you’re able to control depth of field and convey movement in your image. The Sirui ND64 – 6 Stop (1.8) Square Filter – 100x100mm is 2mm which and 100x100mm and can be used in the Sirui 100mm Filter Holder with CPL or other 100mm holders like NiSi, Lee and Cokin. It’s made from German manufactured Schott Plate Glass B270 with exclusive lens coating process, allows many ultra-thin layers of coating to be placed on each glass surface to insure perfectly linear, uniform reduction of light from edge-to edge, maximum light transmission, reduced reflections and precise colour rendition. The ND filter features a Protection Coating (waterproof, oil-resistant, scratch-resistant, anti-reflective, anti-static) for easy cleaning and superior lens protection.