That is a lightweight and tough aluminum 17T pinion gear with special coating requested superlative durability. Optimized enamel design decreases energy loss and noise.
Appropriate Chassis
TT-02, TT-02 Type-S, TT-02D, M-07 Concept, MF-01X, F104, RM-01, DF-02, TT-02B and CR-01 Chassis