UO nebular filter. I've had this for a number of years and believe it was called the Mark V visual when I purchased it. In terms of transmission it appears to me to be narrower than a Deep-Sky filter but not as narrow as a UHC. I have recently purchased an OIII filter and don't see myself using this anymore.
Very good condition. Standard 1.25" threads. $25 shipped within CONUS. Cashier's check or money order preferred. Personal checks must clear before shipping. Thanks for looking.