The Tactical Crusader PROA1 Propane Adapter is made of Metal and is designed for easy filling of gas gun magazines. Simply add silicon lubricant, attach to the top of a standard propane can and fill the same way as you would if you were using a green gas canister. This allows the user to cut down on their spending without worrying about sacrificing performance, which means more money to spend on more guns and accessories. It is important, however, to always remember to add the needed silicon lubricant when using propane instead of green gas.