ok..lol that question..

anyway..there is a few things

1. AEG is eletric..don't need gas
2. Green Gas mag to hold gas
3. CO2 Mag to hold gas
4. HPA Tank to hold gas

2 needs green gas or propane+silicon tank
3 just replace the 12gram co2
4 needs a HPA tank, if you find your gun has a nozzel for air..it's probably a HPA