GBB magazines are made for replicas that work on gas. At the GBB magainze you also stop gas inside the magazine alongside the BB's. However, you have to take into account that the magazines are real cap / mid cap because they can shoot only a limited number of BB's with the gas inside the magazine.
At CO2 magazine you put a CO2 cartridge in the magazine next to the BB's, but you have to take into account that you can only use a CO2 cartridge once.
Gas and CO2
QTAC always has a large stock of gas and CO2 cartridges so you are always ready to go on the field.