Our Automotive Interchange Quick Connects have plated steel or brass couplers with hardened steel balls, stainless springs, and Buna-N seals. The nipples are heat treated to reduce wear on critical mating surfaces and the maximum working pressure is 300 psi in all sizes. The brass are non-sparking and provide greater corrosion resistance than the steel, but being a soft metal the brass will wear much more quickly than the steel.