Is the Speed of Light the Speed Limit?

The speed of light minus Planck's constant multiplies something that makes units consistent. I suppose my answer depends on whether or not charged particles have mass. And I'm honestly not sure if they do or not. If they are massless, I would guess that they travel at the speed of light. But if they do have mass and their mass is non-zero, I would say they travel a significant fraction of the speed of Light.