M: Metric ISO
Mf: Metric fine ISO
BSP: British Standard Pipe Parallel Thread (parallel threads)
BSPT: British Standard Taper Pipe Thread. (Tapered pipe thread, cone 55° and tapered 1:16.)
BSW: British Standard Withworth
BSF: British Standard Withworth Fine
UNC: Unified National Coarse
UNF: Unified National Fine