G&G M4 - 2300 Round AEG Hicap DRUM Magazine (Auto-electric wind G-08-170-1).  T

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.

Any 7.4v lipo will work, like a 250mah or 1000 stick should be fine.  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.