The Vixen.
The Tak sits forlorn awaiting the Canon T ring... the one you gave me was Nikon
And Oasis T rings are not exactly off the shelf items
I used the Tak visually - bit of hit and miss because the back focus is STILL an issue even with my new made diagonal... I ordered a proper 1.25 diagonal from Steve Massey, so that MAY clear things up. She's a finnicky little geisha girl