Diff cups

[gowzy]

I recently rebuking my ball diff on my centro 4.1 however I needed to replace the left hand diff output drive , so I ordered a new one from modelsport and it was different from the old One I had in the car , this hAd a pertruding ring which stopped the play in the diff from left to right , the one from modelsport was a flush finish , my question is where can I get this diff part from which has the pertruding ring on it ?

Thanks
Luke