This video will help you decide the decapping pin size you need, which will be determined by the flash hole diameter in your case. For example, when depriming a 5.56 NATO military case, the flash hole diameter is about .080, so you will want to choose the .078 decapping pin. For smaller flash holes around .060 diameter, such as those found in Lapua brass, Peterson brass or some European brass you will need a .058 decapping pin.
In addition, you will see a purple tube included with your reloading die. This is purple VibraTITE #111. We recommend using this on the threads of your decapping pin. Add a touch to the threads and shoulder of the pin where it contacts the shaft. Snug the pin into the shaft with a 3/16th wrench.