The tops have to pass a very stringent test called UL197. They have to withstand the impact from a 1.2-lb. (0.4 kg) steel ball from 21" (533 mm) and a 4-lb. (1.8 kg) pan dropped 10 times from 8" (203 mm). For cooktops - especially commercial ones - "ceramic glass" is better than tempered glass. They both pass the same drop tests, but tempered glass can bow at high temperatures (e.g. if a pan has been heating on the top for a long period).