An XT4-202 male-to-barb fitting made of nickel-plated brass.Material and media: The material the fitting is made of is also important for determining the fitting’s various physical properties, as well as if it is compatible with the gas. Material choices at manufacturers such as Clippard include stainless steel, brass, nickel-plated brass, and plastic resin. Differing media and the application should be considered when selecting the fitting’s material for the fitting. Suitable media may include air, inert gas, water, liquid, and oil.