Hoya PROND 77mm ND 64 (1.8) 6 Stop ACCU-ND Neutral Density Filter XPD-77ND64 The PROND 64 has a 6-stop light reduction equal to a ND optical density of 1.8. Metallic ACCU-ND coating ensures color accuracy and consistency between different ProND filter grades. Set your white balance once and have the same color balance even if you need to change filters due to changes in lighting, or for creative effect. Constructed from Hoya's exclusive clear optical glass that has a metallic ACCU-ND coating front and back for maintained image clarity. One-piece aluminum ring adds durability and rigidity for assured use and helps to prevent filter jamming.