The Ocean Reef high performance balanced diaphragm 1st-stage regulator is specifically designed for use with the Neptune Space Full Face Mask (see SKU's: OEDNSG, PCKNSG, OEDNSGK). The regulators use a diaphragm design to create an environmentally sealed mechanism to ensure durability and high performance even in contaminated water. The balanced diaphragm, chrome plated marine brass first stage regulator is inherently environmentally sealed. The benefit of this type of first stage design is that none of the delicate internal parts are exposed to contaminants such as salt, sand, chlorine or pool acids. These environmental contaminants can cause corrosion and mineral deposits to form on the internal mechanism deteriorating regulator performance.