Shown installed here, but to replace the spider and bearings remove the circlip and strike it at the indicated point, holding the UJ in the other hand, to knock the cup out a bit at a time. Using grips to twist it out the rest of the way was surprisingly difficult given how easy it was to knock it out. If you are replacing the UJ you can knock it out all the way, but if refitting it be ready to catch it, or do it over a clean surface. Don't strike it near the edges of the hole the cup sits in as you could distort it.
Undersized nipple in the UJ.
It's in 2-parts ...
... so the nipple proper can be unscrewed leaving the base thread pointing straight up.
Undersized (top) and standard (bottom) nipples, with a drilled adapter stud screwed in to the latter.
Adapter screwed into the nipple body on the UJ. No ball and spring seal on this as it is only fitted for greasing, the undersized nipple is refitted for normal use.