Regulators not designed for cold water use are especially prone to freezing. Our simple yet extremely effective Freeflow Control Device (FCD) contributes a significant advance in diver safety. In the event of second stage freezing, free-flow can cause catastrophic loss of air. With the FCD fitted to your regulator, a simple sliding action allows the diver to isolate the free-flowing second stage and continue the dive using a secondary air source or alternatively, the diver can manually control the air flow allowing a safe ascent to the surface.