This is an optional Electrix Metal Transmission Gear Set, and is intended for use with the Electrix RC Circuit, Ruckus, Boost and Torment vehicles. Each set OOffers increased strength compared to the stock gears providing a perfect complement to higher demanding power systems. Each metal gear set comes as a complete package providing a complete solution with only one item to purchase. The differential is a complete differential unit which simplifies the installation and gives the driver a complete second differential as a bonus.fitment ECXX BoostECXX CircuitECXX RuckusECXX Torment