The MK25 EVO DIN300 First Stage is a balanced piston design built for fast breathing response and high airflow across water temperatures. It uses SCUBAPRO's patented Extended Thermal Insulating System (XTIS), which isolates the mechanical elements of the first stage from cold, increasing freezing resistance by 30% over earlier MK25 versions. It is sold separately from a second stage in a DIN300 fitting, allowing it to be paired with a second stage of choice for a custom regulator build or as a replacement first stage.