Most downstream demand valve regulators are calibrated during manufacturing to a single, 'middle of the road' operation. Whether finning up current at 100+ feet or merely snorkeling out to the dive site, this factory adjustment may not be optimum for the wide variety of demands we place on our equipment. A simple twist of the GT 3's adjustment knob enables complete control...set the inhalation requirement to near zero when you need ultimate performance, or tune it for greater resistance 
as conditions or preferences change. A common objection to adjustable second stages is that divers can't imagine themselves twisting and turning a knob as they descend and ascend through the depths. If inhalation resistance is set near zero at depth, your ascent would require you to manually increase resistance as ambient water pressure is reduced to prevent free-flow. Taking another stride beyond common second stage engineering, Oceanic designed a patented DYNAMIC ADJUSTMENT feature into the heart of the GT 3. This mechanically balanced valve maintains a preferred breathing resistance throughout the dive. Set it once and the GT 3 automatically adjusts to make breathing as easy at 100 feet as it is at 30 feet - with no additional manual adjustment.