The Systema PTW series of professional airsoft guns are arguably the best AEGs you can get out there. but in terms of customizability they are limited by one aspect: The battery.

The battery on the Systema PTW M4s is proprietary and although it utilizes a Tamiya connecter plug that is found on many automatic electric airsoft guns other batteries require extensive modification to use, and must often be housed externally, damaging the outlook of the gun. A smaller sized battery may fit into a hand-guard or other type of stock but would have a much lower capacity than the original battery.

The problem with the current, stock ECU (or Electronic Control Unit) is that it is simply too long and too big to fit anywhere else on the gun. Our in-house expert airsoft technician has remedied that with his own ECU. The new, miniaturized ECU is less than half the length of the original and does the same job with equal efficiency. The new and compact size is achieved by effectively folding the design of the long printed circuit board of the original in two, and mounting them carefully on one printed circuit board.

The new ECU fits into the stock tube of the standard Systema with enough room to spare for an 11.1v triple stick lithium polymer battery. This allows for fitting of aftermarket stocks such as the venerated Magpul UBR, which is thin and doesn't have room for what would normally be the Systema battery.

Switching from a 12V Nickel-Cadmium battery to an 11.1v Lithium Polymer battery doesn't have any effect on the guns performance due to the ECU normalizing the voltage and controlling the gun's rate of fire.

The Airsoft Surgeon Mini Electronic Control Unit is a must have for those who want to differentiate themselves from the rest of the Systema crowd by having their own, completely personalized stock.