 E17 is also sometimes used, especially in small table lamps and novelty lighting, and occasionally the lights on newer ceiling fans.Christmas lights use various base sizes E17 for C9 bulbs, E12 for C7 bulbs, E10 for decades-old series-wired C6 bulb sets in the U.S., and an entirely different wedge base for T1¾ mini lights.For a short time early on, these mini lights were manufactured using E5 screw bases.