A generic R100-series receptacle for the 100 mil (2.54 mm) grid with a solder-cup termination. It is pressed into the fixture's probe plate and the spring probe seats in it, so probes are exchanged during maintenance without any wiring work.
100 mil is the workhorse grid for in-circuit test, and the R100 pattern matches the standard 1.7 mm drill used by branded 100 mil bodies, so a plate laid out for one takes the other. The solder cup is the default for a hand-soldered fixture; within the R100 range the numeral marks the body length variant, so check the overall length against your plate stack before substituting one R100 for another.
Generic R100 series, for 100 mil (2.54 mm) test-point pitch
