some take different wrench sizes, but I don't think I've ever seen one that didn't have the same 8mm threads.

This has Ritchie titanium bolts because that was what I had in my junk box. I just scored a pair of dust caps for it. I bought a bag of parts on eBay for $17. It had two sets of those caps and some Bullseye pulleys in it, so I'm happy.