The Hollis DC2 1st Stage Regulator is a compact and streamlined over-balanced diaphragm regulator design that provides progressively greater intermediate pressure as depth and gas density increases for superior gas delivery under the most extreme conditions. The diaphragm membrane transmits the pressure changes to the internal mechanism eliminating the need for the surrounding water to enter the intricate mechanism. The benefit of this type of first stage design is that none of the internal parts are exposed to contaminants such as salt, sand, chlorine or pool acids. These environmental contaminants cause corrosion and mineral deposits to form on the internal mechanism deteriorating regulator performance. The standard diaphragm regulator does allow water into the mainspring chamber so that the diaphragm can perform this transmission of pressure changes. With the DC2 there is a secondary environmental diaphragm membrane that seals off the spring chamber keeping the first stage completely sealed off from the environment adding a second layer of corrosion resistance and the environmental sealing prevents icing of the first stage, allowing the regulator to withstand the rigorous CE standard for cold-water performance. The first stage has 4 low pressure ports (LP) with 3/8" threads and 2 high pressure port (HP) with 7/16" threads. The DC2 First Stage Regulator is manufactured from forged marine-grade chrome plated brass. The compact & streamlined design provides the ultimate control over the internal air path for superior air delivery. The DC2 is Nitrox compatible to 40% out of the box.