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
TRAVELS EASY, BREATHES EVEN EASIER It's the perfect combo for divers looking for top performance in a small-scale system. SCUBAPRO's most compact, high performance piston first stage teams with its most compact, high performance second stage. The result: a top-drawer, travel-friendly reg system that delivers reliable airflow on demand, no matter where your dive travels take you. The MK21 is SCUBAPRO's first balanced-piston first stage to be released since the introduction of the MK25. It is smaller and lighter than the MK25 and uses a smaller piston, but it delivers the same level of breathing performance. The MK21 also provides exceptional resistance to freezing due to the thermal exchange produced by the external fins on its polished chrome brass body. The MK21's innovative "smart" hose layout comes with a standard cap with four low pressure ports angled (+/- 20º) to maximize hose routing. This standard cap can be replaced with an optional cap that offers four low pressure ports at more extreme angles (0°/30°) plus a fifth centralized high-flow low pressure port - a useful configuration for technical diving. The C350 is the most compact second stage in SCUBAPRO's line, so takes up little space when traveling. It is lightweight, breathes smooth and extremely easy, and offers a coaxial-flow inhalation effort control knob and a Venturi-Initiated Vacuum Assist (VIVA) dive/pre-dive switch. The stainless steel front cover frame adds a bit of style. The MK21/C350's size, weight and excellent breathing performance make it a smart choice for recreational divers in general, and just the ticket for dive travelers in particular.
Air-balanced flow-through piston provides constant and effortless airflow unaffected by depth, tank pressure, or breathing rate.
Polished chrome-plated marine grade brass body is close to 20% smaller than the MK25, making it an easy travel companion.
Unique thermal exchange design with external fins optimizes freezing resistance.
Two high pressure ports, one on each side of the body, allow the first stage to be positioned either up or down.
Standard "smart" hose routing cap offers four low pressure ports angled for more convenient hose routing (+/- 20º).
Optional hose routing cap increas- es routing configurations with four angled low pressure ports (0°/30°) plus a fifth centralized high-flow low pressure port, ideal for technical diving.
Redesigned yoke allows for easier mounting on a cylinder, and redesigned cap protects internal components from water intrusion after the dive.
Compact body and exhaust tee take up little space in a travel dive bag.
Stainless steel frame on the front cover adds some style to the compact design.
Classic downstream valve design.
User controls include a coaxial-flow diver-adjustable inhalation effort knob and Venturi-Initiated Vacuum Assist (VIVA).
New dive/pre-dive switch clip makes the assembly more reliable than ever.
Large purge button is easy to activate, even wearing thick gloves.
Holes below the purge button increase water circulation on the diaphragm to improve sensitivity.
Super-flow hose features an oversized bore that allows more air to flow on each inhalation.
Ultra-comfortable orthodontic mouthpiece is easy to grip yet doesn't inhibit airflow.