National Pipe Thread (NPT) is the most common thread for pipes and nozzles in North America. It is different from the thread on a regular bolt and nut because the thread has a taper. These tapered threads are designed to lock together when tightened.
British Standard Pipe Thread (BSPT) is used mostly in Europe and the UK. BEX distinguishes our BSPT nozzles by machining a notch in the hex shaped part of the nozzle.