Mag brand 1000 bb box mag, that has been upgraded by Bingo airsoft works. He added a larger 3D printed resovoir. It should hold about 3k bbs now. He upgraded the motor and wiring to feed faster. Added a door opening on the top to load bbs. And added a side battery compartment, and wired it to jst connectors. This box mag runs flawlessly and keeps up with at least 35 rps. If you want to rain down fire and keep everyone hidden forever without having to reload, than you need this. Only issue is the 3d print has cracked on the front. I remedied this issue with the duct tape. Asking $115 shipped.