RS hubs have a different diameter aperture for the damper to go in (thicker dampers on RS), the bolt pattern for the brake caliper only fits the RS Brembos, which require different brake lines, the bearing is specific to the RS to accomodate the larger flange, that only accepts RS CV joints. In essence, a ball ache for very little gain over the 300mm ST170 brakes which are more than enough to lock the wheels if you disconnect the ABS. Probably a good bit lighter too.