Till today, in threaded connection world it is governed by 2 kinds -- British Standard Pipe Thread (BSP) and National pipe tapered (NPT).
The difference between NPT, BSPP and BSPT seals
TPMCSTEEL brand steel pipe seal
EN / BS hubbed threaded flange - TPMCSTEEL
NPSM vs NPTF vs NPT vs BSPT thread fittings - QC Hydraulics
Technology - TPMCSTEEL
Threaded Fittings NPT Pipe Fittings & BSP Pipe Fittings Thread Type
The difference between NPT, BSPP and BSPT seals
BSP and NPT and other worldwide Thread Information
BSPP, BSPT and NPT thread - TPMCSTEEL
BSPT/BSPP/NPT Male Thread Carbon Steel Hex Socket End Cap Inner Hexagon Plug Oil Hydraulic Pipe Fitting-BSPP thread,3I4 inch 2pcs : Industrial & Scientific