3a 1st end thread class 20 1st end thread quantity per inch coupling half quick coupling, self disconnect, bulkhead half, fuel low anodize surface treated grooved unf 1st end thread series
Used on bell helicopter. 3b 2nd end thread class 4 2nd end bolt hole quantity 12 1st end thread quantity per inch ratchet connector hose half anodize or passivate surface treated un 1st end thread series