This reg system combines SCUBAPRO’s premium diaphragm first stage with its air-balanced second stage. The MK17 EVO is completely sealed off from the elements, ensuring trouble-free operation no matter how cold or murky the water gets. It is more compact yet delivers better breathing performance than its predecessor. Its improved internal design allows more airflow from the LP ports which have been reconfigured for better hose routing. The C370 brings forth the best features of its predecessor, the C350, while adding a balanced valve to its design. Its exhaust tee, based on the S620 Ti’s design, contributes to a 10% improvement in work of breathing over the C350. It’s a smart reg system for all kinds of diving applications.