The Blizzard Pro is the standard for cold water divers during the last 30 years & it has been the go to regulator for many. Public Service Dive Teams around the country and in parts of the world use it because of its reliability at low water temperatures and for its ruggedness. The 9000 Series 1st Stage is a unique and patented design featuring Sherwoods Air-Assisted Depth-Compensation (A2-DC) Technology. A2-DC responds to ambient pressure changes and uses internal pneumatic force to compensate the chamber. The results are an environmentally sealed and dry 1st Stage that is very responsive to external changing pressures. The Blizzard Pro 2nd Stage features Opposite Pivoting Point (OPP).