What are the differences between clay bars?
The primary difference in clay bars is the aggressiveness/grade. There are typically three different grades of clay bar, medium, fine and heavy.
Heavy clay bars are meant to remove deeply imbedded and adhered particles. These will leave hazing and should be followed up with polish.
Medium grade clay bars are meant to remove more stubborn contaminants but may leave behind light micro marring or hazing that will require a follow up with a light polish.
Fine grade clay bars are means to remove light amounts of contaminants and will not harm the finish. These can be used as often as you like and are the kind typically found on store shelves by the likes of Meguiars and Mothers, both of which are my recommendation for most people in search of an affordable, quality clay bar.