Yes it is. I did my Bosch alternator a couple of years ago. I removed the old bearings and went to a local bearing suppliers and they supplied me with some replacements.
I still have the boxes, they were manufactured by 'SKF' and there are 2 sets of numbers on each box, can't remember which numbers they used but they are:-
6201-2RS1 and 189W for the smaller one
6303-2RS1 and 186W for the larger one
I expect those numbers will mean something to the bearing suppliers.