"There are several reputable brand name lights I use and respect, including SureFire, Streamlight and Brite Strike. Another superstar light, and my current favorite, is the ASP XT DF. The DF stands for “dual fuel” as you can use the light with a rechargeable 18650 3.7-volt lithium-ion battery, or if you forget to recharge, it will accept the popular and widely available CR-123A replaceable batteries."