I don't have a picture now, can put one up from an installation if no one has one.
Basically, they are sort of the only game in town if you need power pickup without brushes rubbing on the backs of the wheels, or picking up from eyelets in the journals.
They are ok, not as high quality as the LGB ones, but they are available. I use them for powered cars when I cannot justify the price of LGB (and the LGB ones are shiny, and large and VERY expensive).
These are the wheels with bearings between the axle and each wheel. Not to be confused by putting ball bearings in the journals and both wheels fixed to the axle.
Regards, Greg