CORRECTION!! I just bought the Sylvania 6418 bulb and it is to short. Most of the stuff I've been looking up on the internet crosses to the 6418 which is 41mm long and the Phillips bulb that came out of my trunk is 44mm long. The xf parts list says a C5W and when I look it up it references the 6418. So at the moment I don't know what the bulp number is.