Poseidon 1st Stage Xstream - The cosmetic difference is this first stage is silver color, suitable for all mixtures including Nitrox and Trimix. The Xstream first stage uses a unique synthetic ruby sphere that virtually eliminates high pressure seat wear that is common in knife edge design seating systems. The Xstream first stage also uses a rolling diaphragm design that eliminates any restriction in movement, which creates a smooth transfer of gas from the first stage to the second stage. This rolling diaphragm design further creates a insulating barrier so there is no need for an additional environmental kit. The Xstream has five low pressure standard 3/8-inch UNF ports and two high pressure standard 7/16-inch UNF ports.

Please note that when this first stage is sold "raw" as received from the factory and not as part of a package that includes a second stage, it will have four of the five LP ports plugged (i.e. one LP port will be open) and both HP ports will be plugged.