These are high quality Astrodon Photometric Sloan filters left over from Special Orders and over production. Many are types and/or sizes not commonly in production.
These are new, high quality Astrodon Sloan Photometric filters that are being closed out because they are 1st generation, odd sized, left overs from special orders, etc. These are now 50% off the already heavily discounted price! So here is your chance to score some bargains!

NOTE: In Astrodon part numbers we pronounce the ' character (apostrophe) as "prime" and the _ character (underscore) we pronounce as "sub"). So u'2_27R should be read as "u prime 2 sub 27 R".