BW 82mm AUC MRC Kasemann Circular Polariser Filter. The high-end polarising foils of the Kasemann-type filters are neutral in colour they have a higher efficiency than conventional polarising foils & they are cemented between high-grade plano-parallel optical glass. The resulting sandwich is then precision-polished again to achieve highly accurate plano-parallel surfaces. Subsequently they are edge-sealed to protect the foil against humidity. Brass mounts made on CNC-controlled machines ensure precise seating on the lens. Discriminating photographers regard the BW Kasemann-Type Polarising Filter to be the very best of all polarising filters. They are well suited for applications that require the highest possible imaging quality especially with high-speed telephoto lenses & apochromatic lenses. Why BW over other filter brands. BW filters have been made with Schott glass which guarantees the very highest glass quality. Good quality cameras & lenses are a major investment & at BW we believe that if you should have the best quality filters. Theres no point in buying an expensive optically superior lens only to put a piece of inferior glass over the front of it BW filters are also coated with state of the art coatings BW are the first filter manufacturer in the world to offer multi resistant coatings MRC. The coatings are extremely low-reflective & highly resistant to scratching but above all the unique dirt & water-repellent surface makes cleaning the filters easier. BW filters all feature brass mounts designed to fix the high-quality filter glass in position for life. Brass mounts wont bind with your lens thread or other filters a major advantage over cheaper filters.