this will need 2 holes cut on both sides into a standard 300rd hicap m4 AEG magazine and hot glueing into place. see pics.
the mag will stick out of the bottom minimally so the pull string or winding wheel is exposed. more so on a 400+ hicap.
if used with a 300rd hicap, it would hold near 1800 bbs in the hopper and mag body combined.
If you would like the files to the 3d printed airsoft toy in the picture, please email me at: alexdeguz @ hotmail dot com