Second stage (mouthpiece + demand valve)

The second stage is the part of your regulator that sits in your mouth. It provides air only when you inhale. You use this piece during every single dive. Most divers carry one primary unit and a backup octopus. This mouthpiece works because it reduces high-pressure air to breathable levels. I once lost a mouthpiece in Komodo in 2018 because the strap was loose. Always check your purge button before you enter the water. A stuck purge button can drain a 12L tank in minutes. Make sure your mouthpiece fits comfortably so you do not bite it during heavy currents.