I was a little laxed on keep my gearbox super clean, and bearings super clean. When one of the bearings starts to create a little heat due to grit in the races, the shafts heat up when the inner race starts spinning on the shaft and the hot shaft will melt the outer chassis halves. As I wanted to do the LEAST amount of work on my mini, ive kept the stock steel pins, these seem to be better for bearings that are starting to 'loose their smooth'. I have been able to find some gritty bearings in the gearbox, and the holes in the gearbox halves have not been affected at all. Remember, nothing is exactly the same, you could run 4 years on the carbon shafts. I personally don't like them for the previous reasons