Question: what is the difference between nominal bore and nominal pipe size?
Answer: The terms Nominal Bore (NB) and Nominal Diameter (DN) are also frequently used interchangeably with Nominal Pipe Size (NPS). Nominal Bore (NB) is European Designation equivalent to NPS. For NPS 5 and larger, the Nominal Diameter (DN) is equal to the NPS multiplied by 25.