The RAVEN R9 Series gas magazines are designed for use with green gas, maintenance gas, or similar airsoft gas that contains a lubricant (silicone oil).
 
Gas Types
Green Gas: This is the standard and most commonly recommended gas type for the RAVEN R9 Series gas magazines. Green gas is essentially propane with added silicone oil, which helps to lubricate and maintain the internal O-rings and seals of the magazine and pistol. It offers consistent performance in typical operating temperatures.
Maintenance Gas: This can also be used and typically contains a higher amount of silicone to specifically treat the seals.
CO2: The R9 series also has specific magazines designed to use 12g CO2 cartridges. These CO2 magazines are better suited for colder weather conditions where green gas performance might be negatively affected.
Red/Black Gas: These are generally more powerful ("hotter") and are not recommended for most airsoft pistols, including the R9 series, as they can cause premature wear or damage to internal parts.