The Cokin 84 x 84mm 0.9 Neutral Density 154 Filter is a solid ND filter providing a 3 stop exposure reduction. This 0.9 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. By slowing your exposure time or increasing your aperture, you are able to control depth of field and convey movement more easily. Neutral density filters do not affect the coloration of the image and are ideal for pairing with other filters. Cokin filters are constructed from CR-39 organic glass and are notably light in weight, have a high resistance to shocks and drops, and provide optimum light transmission for high image quality. This filter measures 3.3 x 3.3 inch / 84 x 84mm and is compatible with the Cokin P filter holder.