Idlers??

[maxxdude1234]

I can easily get one bearing in. The other bearing goes about 2/3's of the way in, but there is a little lump (not shown in the photo) that stops it going any further. The little ring that you described you thought you could see does nothing. The bearing that I can fit in pushes as far up the hole and the lump (which stops the other bearing going in.
I'm going to see if I can dremel the little lump away. Thanks for your help.