It is a simple 5mm high performance LED which has had the head cut down and polished. The LED will now focus better (alledgedly)in Maglite or other similar reflectors. I've got mine in a AAA Mag in which I modified the reflector. I understand they will run happily on lithium AA's or AAA's (As if you can find those in the UK?) and will run for up to 20-30 hours.
Not super bright but a fantastic improvement over the stock Mag bulbs!
Doug