difference between candelabra base and intermediate base 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.