This instructional video demonstrates what the features on your dive regulator do for you. Some, but not all, scuba regulators have diver adjustable knobs or switches. This particular scuba diving regulator has a "Diver Adjustable" Air flow knob which allows the scuba diver to adjust the air flow during his/her dive. It also has a "Diver Adjustable" venturi switch to prevent unwanted free-flow when the regulator is not in your mouth.