I use to use the high output light bulb but the battery lasted only 20-30 minutes and now it last 12 hours.
I updated the tail cap to be a push button where it will turn on until pressed again.
It uses the CR123 lithium batteries from SureFire. They are way cheaper than buying them from a local store.
It fits in the flashlight pocket on my 5.11 tactical pants.
http://www.youtube.com/watch?v=vgSf4n3rDI8