ScubaPro MK25/S600 Regulator 2013 The MK25 first stage is our absolute top performer and is a superior regulator thanks to its ultra stable intermediate pressure resulting in an extremely punctual and constantly high delivery of air.ThIs means instant air flow at any cylinder pressure and water temperature for a real carefree dive. Paired with the air balanced high performance ;S600 second stage,;this system is our top performer. Balanced flow valve provides constant &effortless air flow. Diver adjustable inhalation control enables personal adjustment of breathing effort. Diver adjustable Venturi Initiated Vacuum Assist (VIVA) dive/pre-dive control switch and extra high flow exhaust valve account for easy inhale & exhale.