Original Systema upgrade set of AEG helical gears with high speed ratio. Original Systema part number ZS-02-07, suitable for substitution into Tokyo Marui (including Classic Army, ICS and other TM compatible brands) Version 2 and 3 gearboxes. This covers most major airsoft AEG gearbox types including M16/M4, MP5, G3, AK. Systema Engineering materials are much stronger for longer lasting performance, and the high speed ratio can be combined with quicker motors and higher voltage for an increased rate of fire. Boxed with manuals (in Japanese). The set consists of bevel gear, spur gear and sector gear.