Premium breathing performance in all conditions. Our ultimate S600 second stage regulator paired with an all-rounder balanced diaphragm MK17 for best breathing, even in harsh environments.MK17 FIRST STAGEA high performance balanced diaphragm first stage regulator, the MK17 has been engineered for harsh environments and for use in ice cold water or polluted environments. Resistance to cold has indeed been a key element in the engineering of the MK17.The Diaphragm Technology. Diaphragm-based first stages are environmentally sealed so that water cannot enter the inner mechanism. Bearing in mind that regulators generate temperatures up to minus 30°C due to the incredibly fast moving air and the pressure drop involved, it is imperative that sensitive moving metal parts avoid contact with extremely cold water.Therefore, diaphragm first stages have been the favoured choice of cold-water divers and those working in contaminated or muddy water.SCUBAPRO diaphragm first stages feature balanced technology and are packed with patented features resulting in ultra fast flow to the second stage on demand and a fantastic overall performance.S600 SECOND STAGEA second stage regulator must translate natural breathing behaviour into mechanical reality. A high quality second stage can significantly reduce stress and enhance diver safety by providing smooth, low-effort breathing response, resulting in ample yet controllable quantities of air.The designation balanced and classic downstream are also distinguishing marks for second stages and again imply ultimate flow performance and stability in addition to reliability, simplicity and solid performance.