Tamiya Hop-Up Options 54875 TT-02 Oil Gear Differential UnitOil filled sealed gear diffs have become a standard tuning part for many of Tamiyas performance race cars. This TT 02 version can be used on any of Tamiyas TT 02 chassis variants to further improve the cars tuning options. Oil filled gear diffs offer the user to add different viscosity silicone oils into the differential gears housing in order to change the rate of speed in which the differential gears rotate. The rate of rotation can be tuned