Keeping track of the types of gearboxes and their compatible parts can be a difficult thing to do. Each AEG is operated by a specific mechanical box that is powered by a motor. The different version gearboxes and motor types are selected to fit within each gun based on how it looks, or the space it provides for the mechbox and motor based on it's shape. Each gearbox is a different shape, the main thing that separates each version is the arrangement of the gears and how the motor lines up with the gears. To make things as simple as possible we've created a chart for the different motor types and gearbox version and connected them with the guns that use them.

Exceptions:

• ICS Version 2 Gearbox for the M4/M16 is a split Version 2 design.
• Classic Army and G&G M14 has it's own version gearbox.
• Systema PTW has planetary gearbox design with separate cylinder assembly.
• AEP's are basically microsized gearboxes, typically with 4 gears, and have no correlation with the gearboxes listed above.

One common misunderstanding about gearbox versions and gun versions is that they are often viewed as the same thing, sometimes they are but sometimes they are not. For example, the Echo 1 M14 SOCOM Version 3, this gun is the third version M14 that Echo 1 has made, but it has a version 7 gearbox. Another example, the Echo 1 G36C Version 3 is the third version of G36 that Echo 1 has made and it also happens to have a Version 3 gearbox. Typically when there is a version listed in the title of a gun it represents the guns version number from that manufacturer, not it's gearbox version. Manufacturers release different version of their guns when they change some thing on it. I'm going to use the Echo 1 G36C again, the first release of that gun didn't have metal bushings, but when they added metal bushings they released that gun as their version 2 G36; both the version 1 and version 2 Echo 1 G36C's had version 3 gearboxes.