In most cases, key fobs made with vinyl work best with size 20 extra long
KAM plastic snaps. Some people are able to apply enough pressure to get size 20 regular
to work, but for the most part, the extra long is recommended, particularly if you're working with thicker vinyl, such as double layers of marine vinyl.
TIP: Using a hole punch to cut out a hole for the snap (instead of an awl, which only pierces a hole as a needle would) can help. This is because it removes the excess material between the snap pieces. We have hole punch dies here