Recent posts on flashlights got me thinking about my situation. A few weeks ago, I stumbled across this LED replacement bulb assembly when looking for filters. Flashlight Bulb LED Upgrade - 450+ lumens - CREE R5 Single Mode Drop-in - P60 design: Surefire, Hugsby, Etc. - Amazon.com I own several Surefire G2 Nitrolon flashlights because they were economical, put out a good amount of light for their size, and were rugged. If you are unfamiliar with the G2, here's a video: In the years since then, the Nitrolon line hasn't really kept up with current technology, and Surefire stopped making them in different colors like they used to. Now they make a different version of the Nitrolon, the G2X, available for twice the price as the original. Amazon.com: Surefire G2X Tactical Single Output LED Flashlight, Black: Sports & Outdoors For the price of the unit, I didn't think I was expending a lot of cash to see if the unit performed like it was supposed to. So when I got it in the mail, I put it in one of my G2's, and tried it out. It was definitely much brighter than the incandescent bulb, when I set them side by side. Lacking a lumen meter, I can't say exactly what the output is. The spot in the middle is crisp and clean, yet it still has the same nice flood light that the original bulb assembly had. Installation was straight forward. When the unit arrived, it had two springs on it's tail. The instructions found on Amazon.com explained that this must be removed for Surefire lights. It wasn't hard to do, the spring pulled off with only a little effort. When installing it in place of the old P-60 assembly, it seemed to be just a little short- the lens was fully tightened down and the light would not come on. The LED light assembly is made in two pieces, and the reflector is threaded onto the outside of the main housing. I unthreaded it a little bit, pulling the CREE diode a little bit back from the reflector opening, and reinstalled it. The lens assembly locked down perfectly and the light illuminated. I decided to test the unit for heat, as this is a polymer flashlight. I turned it on, and after 30 minutes, checked the outer bezel's temperature. It was only warm to the touch. It was cooler than if the P-60 bulb assembly was installed. One thing that worried me for a moment, was that after about 20 minutes of continuous running, the light went to about half output, making it about the same brightness as an incandescent P-60. After I replaced the batteries, the unit went back to full brightness. Perhaps this is a safety feature, to keep the unit from just switching off immediately when a certain voltage threshold is met? I've had CR123 lights go out without warning when the batteries were dead, and this would definitely be a welcome warning that the cells are getting low. I don't know how long those batteries have been in the unit, and the only amount of data I have on battery life is what was on Amazon.com's review saying that the battery will last 2-3 times longer. Since I don't feel like burning up two of my CR123's just for the sake of argument, I'll wait to test battery life the next time I'm out walking around in the dark. The LED assembly is supposedly rated for a nice, wide range of voltages. A 3.7v- 18v range means that you can safely use rechargeable CR123 batteries without burning up the unit. This is nice, as the standard Surefire P-60 unit is NOT covered if burned up by rechargeable batteries. Here's an example: Amazon.com : Card: Tenergy 4 Pcs RCR123A 3.0V 900mAh Rechargeable Li-Ion Protected Batteries w/ Smart Charger : Electronics I've used these batteries in an Olight T20 for years. They run well, and recharge quickly. According to Amazon.com, and witnessed in real life, is: "Replace CR123A primary cell in most devices, but not good for certain flashlight and camera due to higher open load voltage." Having the advantage of using rechargeable batteries is a BIG plus for me. Yes, I kept the P-60 assembly and put it away JIC I didn't like the LED, or the LED unit fails. And the same company offers units that are multifunction; high-med-low-strobe-sos. I just didn't feel the need for this feature.