MadBull Airsoft just released the XG02 propane adaptor which is priced similarly to the previous version. Those who want to save up on the GBB gas cost can use propane instead and you can handle propane by using this latest adaptor released by MadBull. It's cheaper this way as there's a wide availability of propane and can be easily found in many stores near you. Just don't forget to clean your barrel after each use since propane doesn't have any silicone additive to protect your internals.