What size is that British plumbing fitting you're trying to replace? What about that BSP fitting you just received -- is it the size you ordered? How can you tell 1/8 BSP from 1/4 BSP without a micrometer or a trip to the hardware store?
Thread Detective® to the rescue!
The BSPP Pipe Thread Thread Detective has 5 special steel fittings, each with a different BSPP (British Standard Pipe Parallel) thread size. Each size has both male and female threads so you can identify male fittings and female ports. They are all strung together on a wire lanyard. One end of the lanyard has a small metal tag with an 85mm (3 3/8") ruler with both metric and SAE markings. The fittings are separated by shatterproof plastic dividers, and each fitting has its thread size permanently printed in bold numbers. Loops at both ends of the lanyard let you hang it near your workbench or in the trailer. The extra-long lanyard lets you reach into tight places when removing the mystery fitting isn't practical.
This BSPP kit covers the most common parallel-thread pipe sizes found on British cars:
1/8-28, 1/4-19, 3/8-19, 1/2-14, and 3/4-14 BSPP