A second stage regulator must translate natural breathing behavior 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 imply the same general attributes like first stages, i.e. ultimate flow performance and incredible interstage pressure stability in addition to reliability, simplicity and solid performance.
Air-balanced valve technology
The air balanced valve technology of SCUBAPRO second stages features a balancing chamber in the second stage mechanism, slightly offsetting the force of the downstream air entering from the first stage. This allows reduced spring tension and decreases the inhalation resistance to the lowest possible level. The result is an ultra-high airflow that remains exceptionally stable under all breathing conditions. The air-balanced valve technology is featured in our A700 and S600 second stages. For optimum results they should be combined with balanced first stages, like the MK25 or the MK17.
Optimal Flow Design technology
The Optimal Flow Design valve is the ultimate evolution of the classic downstream technology. Unlike this one the OFD valve features a full length piston shaped to obtain the optimal aerodynamic performance. The gas flows freely over the piston surface and provides the diver with the best breathing experience. No regulator part slows down the airflow, and even the valve spring is shifted to the back side of the piston so that the air doesn't have to flow through the spring coils. The airflow is huge and rich but always under control. This technology is featured on the C300 and C200 second stages.
Classic downstream valve technology
Classic downstream valves are particularly noted for their legendary safety and reliability. When in use, the downstream valve opens in the same direction as the incoming airflow. To close the valve and stop the airflow, a spring counteracts the force of the incoming air. Therefore, a certain inhalation effort is always required to overcome the spring tension and open the valve. The classic downstream valve is featured in the SCUBAPRO R-Series, here "R" is synonymous with robust and reliable. This valve type is found on the R295, R395 and AIR 2