This TSO C103 approved mask is a crew mask assembly including the standard re-breather mask, flow indicator, and a preset plug. These plugs are preset based on customers altitude request up to 25,000 feet. The PB-1 style fitting is typically associated with Cessna aircraft 1980 and newer, as well as pressurized Cessna aircraft pre 1980 and many other types of aircraft. Please use the gallery photo to verify your outlet connector, and select the proper connection above. 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.