These are very smooth and have been handy for designing pendulums.
For my purposes the little threaded nub is in the way, so the obvious choice is cut it off. Bad news is the bearing cage is plastic and the cutting process makes it hot enough to fail. Good news is a damaged bearing needs to be opened up to provide this learning opportunity.
I anticipated small bearings, but I've never seen balls this small before. Pencil tip in the photo to show scale.
