Believe it or not, the original bulb in my 25 year old lava lamp just went out. Initially I replaced it with a standard 40W bulb (Type A), but the temperature of the burning bulb did not match the original temperature. So the lava was not moving and "flowing" as it had been for the previous quarter-century. After some research, I settled on these bulbs even though they cost almost twice as much as regular 40W incandescent bulbs. So far I'm not disappointed. While I can't comment on durabilityβ¦