This listing is for one set of Aeris Ion regulators for scuba. The 1st stage is an AT600. These regulators are used, but in fine condition there is minor corrosion on the yoke knob, and signs of light use over the res of the set, but nothing glaring. We do not know the specific item history so these should be serviced by your LDS prior to any scuba diving activity. These will ship as shown, with the 1st stage, 2nd stage and octo.