This is similar to the M4 AEG Flash Magazines made under the "Lonex" brand. This high-capacity magazine for Tokyo Marui-compatible G36 AEGs also features the quick pull wind-up mechanism rather than the standard windup procedure allowing you to do pretty much a tight wind without having to wind the gear several times. This immediately allows you be ready with another stream of BBs to fire in tight situations.

This is avaliable now at EB Airsoft for US$17.78, free shipping included.