When the sleeve is used for a 5-mm shaft it makes up the difference, so the stock shaft is a drop in fit. But since the stock shaft is a soft metal it might not last long do to the wear on spin downs. I have not tested the life of the shaft, I progressed on using a TRex shaft with sleeve and married a blade cp head which required milling the top of the shaft down to 3-mm and replacing the main bearings to 10X5X3. If I had to do it again I would have used a TRex head also (less work).