26 tpi nut.
Ok, so that other thread doesn't get derailled, What makes a good cup? Who makes a good cup? And what's the best cup for the money? bonus question, who makes the best 26 tpi Raleigh cup (or Italian or Swiss or whatever your favorite oddity is)?
Precision machining and shiny chrome. Lasts forever. I like Magistroni (typically Italian threads).
For 26tpi cups you don't really have a lot of choice. Raleigh, Phillips, and T.D.C. are probably all you will find and they're all pretty much the same quality: nothing special, but plenty sturdy.