The MK19 EVO / A700 takes our extraordinary breathing A700 and pairs it with an environmentally sealed MK19 EVO first stage thats extremely resistant to freezing and fouling of its inner mechanism. The MK19 EVO offers a dry ambient pressure chamber that is equipped with a double spring for optimum reliability, and a LP port swivel turret to maximize hose routing options. The muscular A700, with its precision handcrafted full-metal casing, front cover and valve housing, offers best-in-class breathing performance, including effortless inhalation and an ease of exhalation that is unmatched.