The two most popular propellants for airsoft bb guns is airsoft gas (that comes in cans) and 12g Co2 Capsules. Airsoft gas in cans comes in 4 strengths Duster Gas, which is also called HFC134A gas. This is less powerful than green gas and is used mostly in plastic gas guns. Green gas, which is by far the most popular of any type of airsoft gas, and then we sell red and black gas is for use in cold weather. We also sell maintenance gas to keep your gun in tip-top condition. Co2 Capsules work better in cold weather than green gas, and we also sell maintenance co2 capsules that contain a lubricant and Extension gas nozzles. We have just about every different type and brand of airsoft gas and co2 Capsules on the market, and all at the best price you will find on any site or shop. We have free shipping on order over 50 pounds.