For this high-end polarizing filter the foil pieces are selected individually for maximum color neutrality. Following cementing between high-grade optical glass additional grinding & polishing takes place. This guarantees outstanding sharpness even with very bright apochromatic lenses. The latest cementing technique ensures lasting stability even in damp climates. The new generation of Ksemann High Transmission HTC polarizing filters is fitted with a new polarizing foil which has higher translucency transmission. The BW filter XS-Pro is coated with MRC nano & F-Pro with MRC coating. 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.