You cannot breathe directly out of a scuba tank because of the high pressure. A regulator reduces pressure to safe a level that can be inhaled by the diver. A diving regulator has two parts: the First Stage reduces the tank pressure and connects it to the Second Stage which contains the mouthpiece for breathing
The MC9-SEAL CHAMBER 1ST stage is environmentally sealed, protecting it against icing in cold water and against contamination from particulate matter in silty conditions. When paired with the Ellipse Balanced second stage, which includes an internal heat exchanger, this regulator is an excellent choice for divers exploring the most extreme cold water environments.