This is the Atomic Aquatics Z3, Z2 Brass First Stage w/SS Piston 7 Port Fixed Cap Features: First stage materials are chrome plated Brass and 316 Stainless Steel Atomic Jet Seat high-flow piston first stage Optional factory-sealed first stage to prevent outside contamination such as silt and sand Nitrox ready for mixtures up to 40% First stage ports available in 2 HP fixed / 7 LP on fixed capc *Available in DIN or Yoke, Sealed or Unsealed *A sealed 1st stage will provide protection when cold water diving and protection from sediment entering the 1st stage, highly recommended! The Z" designation is represented by the use of Zirconium as plating material for the precision machined Brass valve body. Atomic developed a Zirconium over Chrome over Brass plating process to deliver corrosion-resistance 3-4 times that of conventional chrome plating. The Z Series second stage lever, orifice and spring are Titanium. Designing affordability doesn&';t mean using shortcuts The Z Series is our most compact and economical regulator system. But its rare combination of performance, ergonomics and materials is unmatched by competitors at any price. The Z Series gives divers the assurance of the same Limited Lifetime Warranty as all Atomic regulators. "