Now, this is a good video for those who just have taken up airsoft as a hobby and they encounter the power sources for gas blowback airsoft guns. Tim of Airsoft GI explains about Propane and Green Gas in just two minutes... "Many new players question what gas they can use in their gas blow back airsoft guns. In this episode of Back To Basics, Tim will explain the two main types of gasses used in airsoft and what exactly sets them apart."