The quick-release couplings of the O series are made in brass and then they are subjected to a superficial passivation to increase their resistance to the environment. The inside parts are all made in stainless steel AISI 303. The accordance with the ISO 7241-1B standard of these couplings assures their interchangeability all over the world. The brass quick-release couplings are mainly used with not very aggressive fluid like fresh water, water and glicole, etc.