Go out shopping for Christmas lights this season and you'll come across mini lights, LED lights, C7 big-bulb lights and C9 bigger-bulb lights. What you won't find is grandma and grandpa's C6 lights, with good reason. Those C6 bulbs were bright, lovely and festive, but insanely hot. In the words of the folks at FamilyChristmasOnline, they "got hot enough to set fire to anything combustible if left in contact long enough." When the paint chipped off of these bulbs, as it tended to do frequently, they let loose a glaring white light that not only overwhelmed the color of the rest of the bulb, but would singe anything it came into contact with. These bulbs eventually gave way to the cooler-burning C7 bulbs that looked just as lovely, but also burned fairly hot. Manufacturers still advise turning them on their bases so their bulbs don't come in contact with a tree's needles and set it ablaze. The large C9 lights are just bad news for indoor use altogether and best kept outside. All of these varieties started to take a backseat during the 1970s when smaller, cooler and more energy-efficient mini lights came into vogue. They're still a pain to fix if a bulb goes out in a strand, but a 50-foot string costs just $1.38 to operate for 300 hours, compared with $8 for a C7 strand of the same size, according to Consumer Reports. The biggest threat to the big, hot bulbs, however, is LED technology. While more expensive in stores than their incandescent brethren, LED lights burn for more than 4,000 hours compared with less than 2,000 for standard bulbs, cost 14 cents to operate a 50-foot string for 300 hours compared with $8 for C7s and $11 for C9s, going by Consumer Reports figures. Incandescent bulbs may be brighter, but the cooler-burning LEDs give owners a better shot of preventing one of the 300 fires and 14 fire-related deaths caused by Christmas lights on average each year. Even worse for the big bulbs, the LEDs even come in faux C6, C7 and C9 styles, reducing those original firestarter bulbs to dangerous relics.