THIS IS A BEARING. It seems a LENCO one, very heavy built.
the 5005 bearing and spindle are not plastic, but the bearing seems just "pressed" in place ( with a hit of a hammer:-).
I noticed that if I turn the bearing a little, it doesn't move, but just for a while. After a while it moves againg. I could try to turn the bearing a quarter of turn and see if it stays still....
Loris