SCUBAPRO MK2 EVO/R105MK2 EVO First Stage A totally evolved classic downstream piston first stage, now more of a work horse than ever. With increased breathing sensitivity and better airflow, freezing resistance is dramatically increased. Check out the new MK2 EVO! THE CONCEPT New XTIS (Extended Thermal Insulating System) with mechanism fully insulated from the environment Increasing freezing resistance by 50% Airflow increased by 15% Larger piston (1. 6mm) for better