I have some old lights that I've been wanting to use with new bulbs, but many LEDs and CFLs have a wider base than the old bulb. This means that when the new "wide" lamp is fully screwed in, the bottom electrical contact will not make contact with the bottom of the socket. These extenders fix this by giving the bulb a little more "reach" for the pins to seat properly. It's inexpensive and works great. Note, however, that it also lengthens the lamp somewhat, which can cause gap issues in some applications.