Nisi?s MC UV series ultra-thin filters adopted a special technology of double-sided, multi-coating, the lens employs high quality Japanese optical glass, which assures high transmittance and highly smooth surface and avoids unnecessary reflection. Meanwhile, the frame using the high quality aluminum frame (with the thinness of only 5.2 mm), it?s the thinnest in the world so far. Additionally, superfine dull polishing and elaborate knurling make sure that the frame will not blanch because of repeated rotation; this ultra-thin filter frames to help avoid vignetting on super wide-angle lenses. All materials used in this filter meet the requirements of the European Union?s standards of environment protection?ROHS(Restrictions on Hazardous Substances), they contain nothing hazardous. Furthermore, the screw thread in front of the frame makes it easy to install the lens cap and other accessories.