Short HG type Driver for Halo MT-SS/MXRC hubs
Supa-Drive system, Alloy HG carrier with Cro-mo pawl and driver unit.
Sealed bearing type.
Technical Infomation
The lightweight bushed driver system was originally implemented into the MXRC hub to minimise the weight of the rear wheel for racing. However, several riders found the bush system was susceptible to excessive wear when compared to a  bearing system, therefore, we have introduced the slightly heavier (15g) cartridge bearing freehub. 
The newer style complete cartridge bearing freehub is retro-compatible with the original MXRC rear hub with a bushed driver, but, due to the altered internal spacing of the sealed bearings, you MUST USE the specially shortened thread HG type lockring (supplied with the sealed bearing freehub).
Caution: DO NOT USE a standard lockring on the newer sealed bearing freehub, as it will not clear the outer bearing.