Many airsoft guns use compressed gas such as CO2 or green gas to fire a BB. Airsoft megastore carries a wide selection of green gas accessories and 12g CO2 cartridges for all of your airsoft needs! We also carry propane adapters, allowing you to use easy to find and inexpensive propane instead of green gas. All of our airsoft CO2 cartridges, gas adapters and accessories are backed by our industry leading 125% LOWEST price guarantee!