Halon can no longer be legally manufactured in most countries due to the damage it causes to the ozone layer. It's still legal to possess, though. Halotron was developed to replace it, a more earth-friendly substitute. Supposed to be very effective, but hasn't been around that long to truly say if it's as good. I suspect either would be just fine for dealing with small fires, and neither would be suitable for larger fires (since the size of these extinguishers is usually limited, especially in a small car like ours).