I have what seems to me a rather odd question. Hopefully this is the right place to post it. Some time ago I purchased a TC bundled with a step-up ring for the SEL 55-210. I recently discovered the ring had been literally glued to the TC, presumably to keep it permanently in place. Not a terrible idea I suppose, but I wanted to remove the step-up ring. So after some difficulty I eventually managed to work the ring off. There is quite a bit of residue left behind and I would like to remove this. Any idea for a fluid I can safely use that might remove whatever bonding agent was used without damaging the ring or TC threads? I tried rubbing it off but I can see that might take considerable time and effort and probably not get it all. I wish I knew what glue/cement it was for certain; it feels a bit rubbery between my fingers, and there appears to be a bit of red coloring to some bits, but only in a few spots. I would be very careful to keep any cleaner I attempt to use on the outside edges of course, and try it on the ring threads first, but the safer the substance the better. I think the TC and ring are both made of a very hard plastic. My first thought was fingernail polish remover but after reading about the damage it can cause to all kinds of things especially plastics, that does not appear to be a good idea. I saw lighter fluid suggested somewhere - not sure about that either. So mainly just looking for ideas if anyone here has knowledge on this sort of thing. If I cannot be sure using something will not damage them, I will resign myself to leaving things as is, but if there is something safe and preferably easy to obtain I would like to try removing the residue. I could stop by the one local photo shop here in town and see if they have any bright ideas, but I do not believe they normally do repairs or lens cleaning so they may not know much about this either.