Shimano Disc Brake Adaptors are the finest disc brake adaptors available for Shimano disc brakes. Utilizing an extremely stiff aluminum construction, you will achieve your proper brake alignment and optimum function. This adaptor is for mounting a standard Post Mount caliper to a Post Mount fork to use a 203 mm disc brake rotor. This adaptor is designed to fit a 203 mm rotor on forks with a 180mm native brake mount configuration (forks that run a 180mm rotor without an adaptor). Use all Shimano brake components for the best braking performance.