Shimano RT64-SS Center Lock Disc Brake Rotor Shimano SM-RT64-SS Disc Brake Rotor with External Lockring – 140mm Center Lock Silver. The Shimano SM-RT64 disc brake rotor delivers powerful and consistent braking performance in all riding conditions. The Center Lock mounting system makes installing and removing rotors quick and easy thanks to the spine mount and lock ring design. Compatible with both resin or metal pads Includes external type rotor lockring