G&G M4 - 2300 Round AEG Hicap DRUM Magazine (Auto-electric wind G-08-170). This is the largest drum magazine you can get for the M4 AEG. Fits in all M4 and M16 AEGs made by nearly all companies. Screw midcaps - get this beastmode mag and dominate the entire battlefield with a smug face.
Includes a 7.4v small lipo that fits inside, then you can charge through the JST balance connection on the outside. Drum has a switch if you want to change from electric-wind to manual wind.
Full polymer build, easy to wind, load, and use. Very smooth function for the most picky airsoft player.