The high performance MK25 EVO air balanced piston first stage is paired with the next-generation D420 second stage for natural breathing and diving comfort in all dive scenarios. The D420's uniquely shaped, ultra-durable fiberglass-reinforced nylon casing allows the LP hose to be connected on either the right or left side for maximum rigging flexibility. Inner winglets within the D420's case direct airflow towards the exhaust valve dramatically improving exhalation effort, while a diaphragm lower in the casing takes advantage of the pressure gradient in the upright position for easier breathing. The Dive/Pre-Dive System adjusts the direction of the airflow right out of the valve by adjusting the thumb tab switch on top of the casing. Other features include a large purge button that's easily operated with or without gloves, a compact Hi-Flow mouthpiece for improved airflow and comfort, and four high-flow and one axial super high-flow low pressure ports on a swivel turret. Made of chrome-plated brass, the MK25 EVO first stage features an air-balanced piston that provides instant delivery of air on demand in all diving environments and all water temperatures, and its XTIS insulated inner mechanism improves cold-water resistance to delay ice formation. The first choice of demanding sport divers and professionals, air-balanced piston first stages are unaffected by changing tank pressure or depth and provide ultra-fast breathing response, instant delivery of air on demand and extra-high air flow. Driven to constantly innovate and improve the diving experience, SCUBAPRO builds flawless equipment for the work, sport, and lifestyle of people whose passion is found below the surface.