6mm Product Reviews present the EFCS version of the Ares Airsoft G36 Metal Complete AEG Gearbox Set. This is a high-quality upgrade for ARES G36 AEGs. Its Electronic Firing Control System (EFCS) and reinforced metal gearbox housing with full steel gears ensure precise, reliable, and durable performance. This 450g black metal gearbox set, featuring EGCS technology and a Control ECU, boosts power and longevity.