It is a multi-bandpass filter transmitting most light in the visual spectrum while attenuating much of the light in the violet portion of the spectrum. Features - Baader Fringe Killer 31.7mm Optically Polished Filter.
eBay
In addition to their special transmission properties, the Baader coatings were developed with another key goal in mind - to reduce the annoying reflections present in other astro-filters. To achieve this, along with excellent out of band blocking, required careful design and testing of the coating stacks.
eBay
In good used condition, I have two that are sold seperatly.
eBay
eBay
Features: Baader 1.25” 500nm Colour Filter Green. TheBaader 1.25” 500nm Colour Filter Green are carefully prepared for amateur astronomical interests the glass are coplaner fine optically polished. Green 500nm bandpass filter.
eBay
eBay
It also enhances the great-red-spot on Jupiter and contrast between the belts and also between zones on Saturn. The dark-blue filter is multi-coated to render reflection-free images. Also, both sides are 7-layer AR coating with only 0.25% residual reflection per surface.
eBay
Baader DSLR conversion filters to replace the factory correction filter ("hot mirror). The special substrate is coated with coatings from the famous Baader. Filter Type: DSLR Astro Conversion. Works With: Canon EOS 7D/40D/50D/60D/70D/400D/450D/500D/550D/600D/650D/700D/1000D/1100D.
eBay