First stage regulator (tank → HP/LP)

The first stage is the metal component that screws directly onto your scuba cylinder. It acts as the primary interface between your air supply and the rest of your gear. This piece reduces the massive tank pressure down to a much lower level for your second stage. You will see high-pressure (HP) ports for your gauges and low-pressure (LP) ports for your inflator hose. Most modern units use a balanced design to maintain consistent breathing even at 30 m depths.

Check your O-rings regularly. I once saw a diver in Koh Tao lose air because a $2 rubber seal perished after two years of salt exposure. Always ensure the connection is tight before you descend. If you feel resistance while breathing, your first stage might need a service technician.