The Mad Bull Propane Adapter V2 made completely of metal and has a silicone oil port to make lubricating the gas easier. The metal construction is more durable than plastic because as the gas flows through the adapter it chills the adapter making it more susceptible to breaking off or cracking.
The nozzle of this adapter is not compatible with magazines with extra large base plates. It will not reach the fill nozzle on guns such as the WE Hi-Capa.
Also, propane is heavier than air, do not use indoors. Propane is poisonous if large amounts are inhaled, and extremely flammable.