This is a set of optional ST Racing Concepts CNC Machined Aluminum Rear Hub Carriers, and are intended for use with the HPI Blitz and E-Firestorm Trucks. Precision CNC machined from high-grade aluminum, these rear hub carriers features a set-screw over hinge-pin design that secures the hub carriers on the hinge-pins. This design reduces wear by forcing the hinge-pins to rotate in the arms and not in the aluminum hub carriers. These parts increase durability and add a awesome factory look to your HPI Blitz