[M] Metric [UN] UNC/UNF/UNEF/UNR/UNRC/UNRF/UNS/... [BS] BSW/BSF/Whit.S/Whit. [ST] Self-Tapping [NPT] American National Standard Taper Pipe Thread [ZM] [Mc] [Mp] Metic pressue-tight joints threads [R] [Rc] [Rp] [R1] 55°Pipe Threads where Pressure-Tight Joints are made on the threads [G] 55°Pipe Threads where Pressure-Tight Joints are not made on the threads