USA series slotted rotors feature a new narrow slow to eliminate wind noise heard when using most sport rotors which means they are noise free from the get go. Black geomet coating leaves a nice impressive finish and protects the rotors against corrosion for the life of the rotors. . Another great feature of slotted rotors is the way they MAINTAIN FLAT AND PARALLEL PAD WEAR and avoid the record grooves or galling common with non-slotted rotors. This improves pad contact and braking throughout the life of the rotor and pad set