These 16mm spring loaded pogo pins are great for programming and applications where you don't always want headers soldered onto your boards. We use them for our programming jigs in production. The pins fit snugly into most standard perf board holes. Solder them just like you would normal wire. This unit has a spherical tip.
Pogo pins are little spring-loaded contacts, very handy for making jigs, or making momentary (but electrically solid) contacts. We use them by the dozen for making programming and testing jigs but they're handy also if say you want to JTAG program a board that you cant solder headers to - just shove these thin contacts into a 0.1" pitch IDC programming cable and press it onto the contacts.
The Pogo Pins come in different Tip styles - flat, conical, rounded, crown, etc. This pin comes with spherical tip. This tip is great for making connections to PCB Test Points, without leaving behind a mark like pointed tips
Pogo Pin Tip Style Selection Guide: Short Selection Guide for Pogo Pins Tip Styles
Pogo Pins P50 series Ordering Guide