This nifty little devil attaches to your E90 with ease. But once on, it can hold and help dish out 1500-2000 rounds of Airsoft BBs, turning your sub machine gun into a lightweight LMG. It utilizes an M16/M4 magazine to help feed and shoot all the BBs, and the roll-away box magazine holds all of them. You can also use the box mag to install a large type battery (9.6 4200mah) with very minor modification.
M4 magazine sold separately and is reguired for use of the box mag