The lightweight, simple, compact R2XR first stage is a classic downstream (aka “flow-by”) piston design by Mares XR. The R2XR has four standard size low pressure 3/8-inch ports and one standard size high pressure 7/16-inch port. This regulator has the typical BSP G5/8 DIN connector that will fit 200 Bar and 300 Bar valves. One of the low-pressure ports now includes the Mares dynamic flow control (DFC) system to provide a constant inter-stage pressure during inhalation with gas flow unaffected by depth, tank pressure, or breathing rate. Tested with oxygen, the Mares R2XR now also includes their Auto Sealing Technology (AST) that stops moisture and contaminating agents from entering the interior of the first stage, as can happen during the surface interval when the regulator is being moved between tanks or post-dive when the regulator is rinsed.