Our Automotive Interchange Quick Connects have plated steel or brass couplers with hardened steel balls, stainless springs, and Buna-N seals (other seals are available on special request). 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.