What are the differences between different base sizes on light bulbs?
The commonly used light bulb bases in holiday lighting are candelabra base and intermediate base. A C7 bulb has the smallest base called a candelabra base and a C9 bulb has a larger base called an intermediate base. For each type of base, there is a corresponding socket size. For example, a light bulb with a candelabra base will fit only a candelabra socket. Therefore, when purchasing light strings, be sure to purchase bulbs with compatible bases. If you purchase light strings with intermediate sockets, be sure that the light bulbs you purchase also have a intermediate base.
