fusion engine kit m249Polarstar's Fusion Engine is a dual solenoid two solenoid system. You can quickly change and adjust the weapon's key functions via the FCU (Fire Control Unit), which is no bigger than an AEG's MOSFET, and can easily fit into the stock of an M4 rifle, for example, along with a small Li po battery. Using the FCU's five position joystick and LCD screen, you will be able to easily adjust functions such as the system's cyclic speed, ROF and nozzle timing