A new ball differential, out even more turning performance! The 20T counter gear makes 2.7 secondary gear reduction ratio. Use with OD2679 Counter Gear Super Low Gear Set (18T-19T / For GALM Gear Drive Set, XEX) brings you to adjust to your liking. The idler gear position is fixed to prevent unexpected troubles. 2.4mm differential ball is create a smooth and non-slip ball differential!