It was a CNC lathe. What my friend and I did (he was the one running the machine) was we took off all the backing weight on the OEM flywheel. basically it's all the dead, non-functional weight that Honda put on the back-side. It's the same place they remove some excess weight for the VX flywheel as well. It's been going on 3-4 years now with 262HP and 213ft/lbs of torque going through that lightened flywheel. Recently inspected, it showed no signs of stress fractures or heat scorching even with a 6 puck sprung clutch kit on it.