My goal was to take a cheap AA flashlight and make it more useful by drilling it out to take 3 CR123 cells and then swap out the bulb for a brighter 7.2 volt Krypton. I chose a $5 Rayovac at Wal-Mart because it had a body big enough for the larger lithium cells. Then I took a 43/64" drill and ground the tip flat. I found that I needed a drill bushing to guide the drill, so I made one of those. That's it on the drill in the pic. The drill left a bunch of polymer "fringe" which I tried to clean off using a hobby knife. The bulb came from Radio Shack and costs about $1. It's 7.2v and 0.7 amp. It's a standard 6 cell bulb. The light output was much greater and much more useful than the original with AA's. I don't have a way of measuring the lumens but I would guess it's probably in the 8-15 lumen range. Which is what I was looking for since I'll use the light to work inside dark machine cabinets. My only disappointment was the life of the batteries. Again I can only estimate but I would say they had a run time of about 20-30 mins. Maybe less. The Surefire batteries seemed to run longer than the Radio Shack ones I started with. Any ideas on how to get longer battery life? I don't know enough about LED's to build one of those to fit yet. Is there a different bulb out there or could there be something about the flashlight circuitry that could be wasting power? I welcome any and all ideas. Again my goal is to produce about 15 lumens of light for close up work in dark machine/electrical cabinets.