M4 - M16 Auto electric wind 2300bb AEG Hicap G-08-170-1
Drum Magazine Fits in all M4 and M16 AEGs made by nearly all companies.
Battery is optional.
Use a 7.4v small Li-Po that fits inside, then you can charge through the JST balance connection on the outside.
Any 7.4v Li-Po will work, like a 250mah or 1000 stick shouldbe fine, max 110mm.