BSP thread stands for British Standard Pipe, commonly used in Australia and New Zealand. It is measured based on water flow trade size rather than the actual diameter, which can sometimes cause confusion when measuring ports. 

There are two types of BSP threads:

• BSPP: Both the female and male threads are parallel.
• BSPT: The female thread is parallel, while the male thread is tapered.

Both types of threads share the same pitch, angle (55 degrees), and shape (rounded peaks and valleys).

• Major diameter is slightly less than the actual outside diameter of the threads.
• Minor diameter is the measurement of the inside of a female threaded connection, from thread to thread.

The table below provides the major and minor diameters for each BSP Trade Thread Size. Note that the minor diameter might be slightly smaller than listed, depending on the specific thread gauge used during manufacturing.