This is the Apeks XTX50 Scuba Diving Regulator Features:First Stage: Unique over-balanced, diaphragm design - as the diver descends, the over-balancing feature allows the medium pressure gas in the hose to increase at a rate faster than ambient. This results in superior performance at depth. 2 HP ports and 4 MP ports are angled for optimum hose routing An environmental dry system keeps water out of the main spring chamber thus preventing ice buildup and keeping silt and contamination out Second Stage: Pneumatically-balanced second stage results in smooth, easy breathing The XTX purge buttons are large and easy to operate. A 2-stage progressive purge is used. Press the purge on the side for a lower flow rate, useful where more control is required such as filling lift bags etc, then press in the center for the full effect of the purge, i.e. when regulator clearing etc. The large venturi lever has a soft touch rubber grip, which makes it easier to locate and use. The lever reduces the amount of grit ingress and therefore resists any possible friction giving a smooth operation. Easy-to-grip opening effort control knob keeps the diver in control The 2nd stage is manufactured with active protection against infection as all molded parts are produced with an additive that kills MRSA, protects against E-Coli, bacteria and fungi, and is also very effective against viruses, mould, yeast and algae. A silicone exhaust valve improves the breathing performance of the regulator The Comfo-bite™ mouthpiece virtually eliminates jaw-fatigue A heat exchanger (patented) which surrounds the valve mechanism, dissipates the cold caused by gas expansion while drawing in the warmth of the ambient water Available in yoke or din configuration The XTX50 is for the discriminating diver who wants the benefits of a feature-rich regulator at a moderate price. This popular regulator has four medium-pressure ports all mounted on a rotating turret. This results in optimal hose routing while eliminating sharp bends in the hose.