Easy to Use - Know your REGs are OK with a Regulator Intermediate Pressure Check Gauge. This handy gauge simply attaches to your BCD Hose. It measures the pressure from your 1st Stage so you can check that your 1st stage is reducing your cylinder pressure to the correct intermediate pressure that's required for correct operation / breathing characteristics by your second stage regulator. Take a few breaths from your second stage and the needle on the gauge should speedily return to the correct intermediate pressure. Can be used to help diagnose faults and helps ensure that your 1st Stage is performing correctly. Helps you decide whether your regulators require servicing / adjustment etc.