HI Dutch bikerbob is probably referring to the two part bush where the inner metal bush is pinned to the outer part that has the flat on it , the pins do apparently sometimes shear allowing the inner to revolve with the shaft, not good, I never did like that idea although BSA and many others find it sound enough, I always use the one part bush, get it oversize and have it bored to suit the crank ( should that be undersize?}