Just confirmed from Phil that RX was designed for Feather Pro and Kai Mild. Dorco, Kamisori, and Kai Regular would also work, but not the Feather Light, either Guard blades, or Feather Super Pro. Now supposedly this razor is supposed to be so good that you wouldn't need anything better than a Pro. For that price though, I would expect a Pro barber to come with it to shave me.