I have a collection of Mini Z mr-01 02 F1. They fit good work well. I was designing the MR_01 in gold and black and wanted gold tone ball bearings but these are not gold or brass colored they are silver also different from Kyosho ball bearings in that the balls are exposed where they are not in Kyosho. This may cause problems in the future with dirt etc getting into them. However should be easy to clean.