The Circuit Sports clutch pivot ball for the S13/S14/S15 SR20DET & KA24 engines uses a S45C mid carbon steel for upgraded strength over the factory pivot
that's known for breaking on most cars that sees repeating clutch kicking
and track racing. Circuit Sports pivot ball was designed also to be
thicker than the Nismo unit which means this is a lot more durable compared to the Nismo unit.