Pogo pins

Spring loaded pins, also known as pogo pins, spring loaded test pins etc, are a neat tool to keep pins pressed against a test point or interconnect point. I intend to use five of them for In Circuit Programming, removing the need for permanent ICP pins in my circuits.

While searching the web for such pins I realized brand name ones are insanely expensive. Ebay to the rescue! As often is, china products are available to fulfill your needs. I found that the most common ones are named P75-something. But what does this something after P75 mean?

I found this image, showing all variants. I went for the P75-B1 which has a very sharp tip perfect for holes in the PCB.