I am not sure as I borrowed it from a buddy quite awhile back when I did my 360 but it was a grit for moly rings & I called flexhone & asked them for the drill speed & # of strokes & how fast to stroke it. They remove virtually no material & smooth out even more the finish from the rigid hone. and you might peruse this site. "breakin secrets" article at www.mototuneusa.com