Christmas tree bulbs, running on a 12V transformer (I think, my note just says "2 volts", so I guess they are in sixes):
The weird thing is I am certain that I asked the same question here about them about 10 years ago, but I can find no trace of that, nor anything in my email for the ones I bought then.
Thanks for helping, we're down to the last two, so I'd better get some replacements in for this year.
Daniele