The new MK25 EVO/D420 Regulator System combinines the iconic design of the original D-series regulators with the latest advances in breathing performance technology. Air-balanced Progressive Flow Control Valve is able to deliver abundant airflow with a natural smoothness comparable to breathing on the surface. 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 case takes advantage of the pressure gradient in the upright position for easier breathing. 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. Backed by a manufacturer's limited lifetime warranty. 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.