And that is an important factor these days I would think.
How good of steel alloy was used in some of the grade 25
bearing balls offered by some vendors these days? Who's to know.

That's why I like old Campy balls and bearings. They were made with great steel,
I think. Though I have no empirical evidence to support that. But having pulled many out of
thirty to fifty year old bikes to find them looking like new, convinced me.