Use: There are many types of metal to choose from. If the part is being used for a critical corrosive application, use stainless steel. Brass is very common for propane or natural gas applications. Common steel can be used to reduce part cost, while the adhesive package can be used to give a protective coating for weathering. Injection-molded metal (which is then sintered) can also be used. In some cases, plastic may be substituted to reduce cost or help with corrosion issues.