Are starter/gen bearings special?

[sbklf]

Purchased bearings at a local supply house. The numbers did not match exactly but thought nothing of it until I noticed the socket that the bearing goes into on the commutator end has two pins almost like dowels in it that would be in contact with the outer face of the bearing. Is there something about starter/generator bearings (possibly from an electrical standpoint?) that makes them different from normal bearings?