Unmatched 98% Average Transmission! Freedom from ghost images (very low reflection multi-coating, Striae-free, and plane-parallel substrate).
Extremely Sharp Cutoff at 680nm (leaves all the visible red, including the important 656nm H-alpha emission line).
Sharp cutoff below 420nm. Eliminates violet halos around bright stars (more effectively than simpler so-called Minus Violet photographic filters).
True optical quality glass substrate and coatings. Why spend all your money on quality primary optics - only to place a lower grade filter optic in the path
Combine with any of the other Baader filters, to deliver the sharpest images possible.