The Xstream second stage is an upstream regulator. The safety valve (OPV) ensures pressure inside the regulator will stay at a point in which for normal breathing in the event of a failure. In the unlikely event that the regulator fails, it will not free flow; it will continue to breathe normally without suffering massive gas loss.
We believes that the Octopus should be as powerful and reliable as the primary regulator. For that reason, the second stage Octopus is the exact same second stage that is used as the Xstream primary regulator. The only difference is the color of the exhaust cover.