The modern airsoft gear box is made from a mechanical system that is comprised of the gears and motor to transfer electrical into mechanical energy to fire the gun. The mechanical energy is transferred to the air system when the piston meets the sector gear.
Does not really fit VFC Glocks unless you are brave enough to do a bit of filing where the stock touches the base of the gun. You can mitigate the wobbling by putting some tape around to make it a tighter fit. I can't speak for other models and how it fits but it does the job for now.