Atomic Aquatics Z2 Yoke Style Regulator First stage materials are chrome plated Brass and 316 Stainless Steel Nitrox ready for mixtures up to 40% Atomic Jet Seat high-flow piston first stage A new high-flow second stage case that significantly lowers breathing effort at any depth from shallow water to beyond the limits Dual material second stage cover enables entire front to be used as purge.