Excuse me for giving erroneous information in an attempt to save a guy time, money, and aggravation. 35 years of owning, building and driving manual transmission vehicles and I really haven’t learned much, my own experiences were figments of my imagination. Somehow the magic elixir of lightweight flywheels and/or sintered iron discs has eluded all the car manufacturer’s engineers & bean counters to the current date, perhaps you could enlighten them. The sintered iron in the sof-lok is very gentle on steel or nodular iron surfaces and shouldn’t scratch it any more than leather, they might start calling it the million mile clutch.