The B34S is a spring-loaded, self-operated regulator available with or without internal relief. It combines the B31 8" diaphragm case with the B34 valve assembly for an economical solution to mid-range commercial and industrial applications. Among its attributes are an adjustable loading ring for controlled boost at high flows, precision breather opening to ensure proper stability under all conditions, and in the R model, a high capacity internal relief valve. All critical parts are either steel or aluminum, not plastic, to ensure reliability.