While I have a couple of the X2's, most of the ones I have on EDC items are the older versions. I find them useful to locate my flashlights and keys. For rescue applications, I have a military version on the back of my helmet, so my fellow rescuers know where I am if I am facing away from them. I also have one on my PFD, so if my primary markers (krill and strobe) are not functioning, there is still some type of marker on my person. While not real bright, on a dark night most of my team members have said they can locate me in the dark. Pete