The first stage of this beautifully machined ST1 comes from a special grade type 316 stainless steel that is twice the strength of brass with corrosion resistance approaching titanium. Many environmental experts around world have classified Stainless Steel as the ?Green? metal of the future. It does not require any additional protective chrome or nickel plating processes that can be harmful to the environment and is 100% recyclable. The second stage features all titanium second stage components as found in the T2 and B2 regulator models. Comes as standard with environmental seal on the first stage