This adapter allows you to use HPA (high pressure air) and M4 AEG magazines on your Hi-Capa airsoft pistol. To use it you will also need an M4 AEG magazine, “paintball” tank with low pressure regulator (0-140 psi), a hose with a Foster (polarstar) quick disconnect and of course bbs. The normal operating pressure for green gas is roughly 120 psi depending on the temperature. We recommend that you run your pistol near this pressure and do not exceed 140 psi. Keep in mind that higher pressures can cause excessive wear and damage to the internal components of your airsoft pistol.