Was wondering if someone could help me out. I did some researching to find out what mount it was and it came up with an M42 mount. I have an X-T1 so I bought a M42 to Fuji X adapter. But the lens doesn't come close to fitting into the adapter. Am I doing something wrong or did I buy the wrong adapter? This is the adapter I bought. http://www.amazon.com/Fotasy-AF42-A...ount+Lens+to+Fujifilm+FX+Mount+Camera+Adapter Here is a site I found for some information on the Rikenon lens. http://www.photographyobsession.co.uk/gallery3/photo-equip/rikenon/rikenon-135mm I also purchased a Minolta 50mm f1.7 and got the adapter at the same time for it and it works perfect.