Lowers harmonic vibrations. Harmonic vibration at the pad-rotor interface is a prime cause of friction induced braking noise.. The Flex-Hone for Rotors reduces high pitched "squeal" and "groan" caused by a peaky, rough turned finish.. More rotors per hone lasts much longer than abrasive pads.. Non-directional finish spiral grooves on the braking surface are a prime cause of friction induced brake noise. Ideal for new rotors, too!. Removes the cut, torn and folded metal fragments from the surface.