GHK 40rds GMAG Gas Magazine for GHK G5 / M4 GBBR

The GHK 40rd GMAG Gas Magazine has a Polymer external housing with metal internals containing a high-flow output valve. Since it was made specifically for the G5 / M4 Gas Blow Back Rifle series, it only stores 40 round 6mm BBs which is quite a lot for a GBB mag and a slot where you insert green gas.