This mask is a passenger mask assembly including the standard re-breather mask, flow indicator, and a preset plug. These masks have a fixed flow orifice in the Plug-In which requires a minimum supply pressure of 55 PSIG at 25K feet (minimum 60 PSIG at sea level). The PB-1 style fitting is typically associated with newer Cessna's manufactured in 1980 or later, this fitting is also commonly used in pressurized Cessna aircraft before 1980 and other aircraft. The flow indicator is a simple to read red to clear indication of positive flow. Please see the outlet configuration in the gallery for identification.