SCUBAPRO's best-selling air balanced second stage and its top-performing air balanced piston first stage is a match made in diver heaven. Well-known for its low work of breathing, year after year this combo has consistently ranked as one of the top-performing reg systems on the market. The MK25 EVO first stage lets you enjoy an ultra-fast breathing response, instant delivery of air on demand, great sensitivity and impressive airflow. The S600 delivers smooth and easy inhalation and exhalation while offering efficient user controls, including a powerful purge, an inhalation effort control knob and Venturi Initiated Vacuum Assist (VIVA). Together they provide a steady flow of air, regardless of depth, water temperature, or workload.