These drill bits are made especially for drilling plastic. They have cutting ridges on the outside diameter instead of traditional tapered flutes to the center. The center has a point for exact hole location. Look at the picture of the black .093" thick kydex we drilled in the "testing lab" (my basement) here at the global headquarters of your favorite knife supply house. You can see the clean holes drilled. Note the hole I drilled half way. You can see the outside of the hole has been cut first. In testing the kydex did not climb up the this drill bit vs. the traditional style bit. This is entirely worth the price of admission. I've lost count of how many sheaths or other kydex parts I've ruined because of how it tends to climb up a bit when drilling.
Get one and promise to only use it for plastic. Better yet, get two.