155F-125 single stage regulators are designed for extra heavy duty cutting, industrial applications, laboratory testing, manifold installations, etc. Single-stage construction. Forged brass body and housing cap. Delrin-cap bushing for smooth adjustments. Self re-seating external pressure relief valve on oxygen, inert gas, air CO2, and hydrogen models. Sintered bronze inlet filter. 2-1/2" gauges for easy reading. 3-1/4" diaphragm. Conforms to CGA E-4 standard for gas pressure regulators.