You cannot breathe directly out of a scuba tank because of the high pressure. A regulator reduces pressure to safe a level that can be inhaled by the diver. A diving regulator has two parts: the First Stage reduces the tank pressure and connects it to the Second Stage which contains the mouthpiece for breathing
The RS-811S features a balanced piston first stage, offered in both yoke and DIN configurations. This compact and reliable balanced piston first stage delivers instant and consistent airflow by way of two H.P. and four L.P. ports. The S-11 second stage features the Advanced Flow System (A.F.S) and a venturi adjustment lever in a compact case design.
First stage (R-800S)
Compact and reliable balanced piston first stage
Instant delivery of air and high airflow for superior performance