From Manufacturer
Offering increased control over exposures, this Pro Ultra Slim ND Filter from Fotodiox features a 145mm front filter thread, and is used to darken the entire image, thereby allowing you to increase exposure times or to work with a wider aperture setting than without the filter while maintaining the correct exposure. By slowing your exposure time or increasing your aperture, you are able to control depth of field and convey movement more easily. The 1.5 optical density of this filter requires a 5-stop increase in exposure to achieve a normal exposure.
The filter is made from optical glass, which has been multicoated to maintain image quality when working in strong lighting conditions. The glass is set in a 3mm-thick anodized aluminum ring that is lightweight, durable, and slim to help prevent vignetting when used with wide-angle lenses.