A ring or labret stud (typically used in a labret piercing) is the piece of jewelry. I have a lower lip piercing, only i use a very small labret stud (not a disc backed stud, but a fish-tail...)
kazza those pics are awesome....i've never thought to look for a pic of the actual bridge over the river kwai, although that looks tiny....i imagined it to be at least half a mile long