Originally Posted by Ex Pres

That schematic is all screwed up. The upper head-tube race shown isn't a race, it's a cup. And it's not going to fit inside of that adjustable "race" shown, which is also a cup.

I've always used the term race for the "inside" contact of the caged/loose bearing, and cup for the "outside". Calling all 4 pieces races just confuses the situation. A threaded headset has a crown race, a lower cup, an upper race, and an adjustable cup. Having clearly definable terminology for each part makes it a lot easier to understand.