 Christmas lighting began with small C6 bulbs — where the C means "cone" for the candle flame shape and the 6 indicates the diameter measured in eighths of an inch, ¾ inches (19 mm).These were on a miniature candelabra screw-base, now designated E10 (Edison screw, 10 mm).Replicas of these bulbs are now produced as miniature strings, usually with the entire bulb replaced, but sometimes with a decorative cover with regular bulbs inside.