AEP MosfetDescription Precisely and professionally made drop in MOSFET system designed for Airsoft Electric Pistols. This system increases the AEP's rate of fire and limits unnecessary battery usage. In automatic fire mode, the piston stops in a random position due to the gearbox design. For proper operation, it is necessary to have a functional gearbox cut off lever, selector plate, reverse latch, trigger, and trigger block, as it has the standard gearbox.