The choice of material directly impacts the fitting's lifespan. Nickel-plated brass is the standard for general industrial use due to its corrosion resistance. For food-grade or chemical applications, you must specify Stainless Steel (304 or 316). If the environment involves welding sparks, prioritize flame-retardant PBT plastic or all-metal bodies. Ensure the internal O-ring material (NBR, Viton, or EPDM) is compatible with the operating temperature and the type of compressed air or gas being used.