This battery extension unit is made for the convenience of the players who own a G&G ARP9 AEG and feel limited in the size and capacity of their battery power source. Due to restricted battery space, AirTech came up with these easy-to-install battery compartment extensions for the ARP9 rifles to allow the use of a bigger battery and relieve a cramped MOSFET unit without having to modify the gun itself. This extension also ensures maximum play time since there is more space for bigger batteries to be used. The specially designed strong nylon build provides optimal durability even in the toughest environments. The holes on the sides of the extension allow for easy installation onto the back of the rifle stock. Upgrade your AEG to maximize its full potential with the help from this BEU Battery Extension Unit from AirTech.