I am very new to the quality flashlight world and this is my first thread in CPF. I just recently purchased a Quark "X" 123² Tactical and I absolutely love this light! I can tell that this will be the first of many in a new addiction of things to spend money on. I have researched what I am about to ask quite a bit and cant seem to find my answer. That doesn't mean my answer is not out there it just means I am new to this forum and forums in general and may not know the best way to look. I know that my flashlight takes 2 CR123's. What I want to know is can it take 2 RCR123's? Or an 18650? Or a 17670? If it can take any of these rechargeable batteries what are the ups and down to using them as opposed to the typical CR123? Any advice you experienced flashaholics can offer would be very much appreciated.