I just bought a new Tacx Flux trainer which has required that I install a cassette on this. Great, sounds easy enough. Purchase a few tools (lockring tool, chain whip) and this should be a piece of cake. All in all, things went ok until I decided that I wanted to try it again. Not sure why I wanted to do that, but I did.

Anyway, in the process the little spacer/foil thingy on the 11 cog broke (no idea how) but anyway, that is ruined so no hope of salvage.

My question is, do I really need this? Can I just go forward and not worry about this? If it is necessary, can I just buy a new lockring or do I need a new cassette. I did a quick search and looks like I can find a lockring with spacer for Ultegra and DuraAce but not 105. I would assume they are interchangeable?