Hoya PROND 55mm ND-500 (2.7) 9 Stop ACCU-ND Neutral Density Filter XPD-55ND500 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 Hoyas 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. One-piece aluminum ring adds durability and rigidity for assured use and helps to prevent filter jamming.