This is a fantastic 1st Stage This super 1st stage features: Balance Piston 1st Stage Delivers exceptional performance Delivers consistent, maximum airflow at vitally any pressure level and any diving depth A unique flow-through piston design ensures optimum flow, even under hard and deep diving conditions Fewer moving parts simplify service, maintenance and tuning A low-pressure port swivel assembly provides versatile positioning of 2nd stage, octopus, inflation hoses, and 2 high-pressure ports allow up" or "down" tank valve mounting Advantage: reliable, easy breathing, high performance Get the same quality without paying the extra price. "