Spare CO2 magazine for the gas blowback G5/PDW/M4 series from GHK. Holds up to 40x 6mm BBs and comfortably takes 1 CO2 capsule for normal operation which will last around 100 rounds before capsule replacement.
Also work with other WA system GBBR.
It CANNOT fit in an Inokatsu or Viper Tech GBBR.