The purpose of this review is to describe additional subtle differences between genuine and fake flashlights. The background story is that I bought this light because I had a handful of CR123 batteries that weren't good enough to drive a smoke detector but still registered reasonable life on a voltmeter -- so I wanted to use those up rather than dispose of good batteries, but I didn't want to be locked into a CR123-only light. I initially bought a light from what looked like a reputable seller on eBay. The light arrived and as far as I could tell, both packaging and light looked genuine. Other reviewers have pointed out that fake lights: 1. don't include batteries 2. don't have a SL logo on the button 3. have a black-colored tailcap gasket (instead of orange) 4. does not have springs on both ends of the light to hold the battery The light I received did not have any of these issues so I felt pretty good about having received a genuine light. However, some reviews also point out that in addition to all of the above, counterfeit lights also cannot be programmed using SL's Ten-tap system, and this was true of my light. When I tried to program the light using Ten-tap, the light would stay on with the 10th click/hold, rather than extinguish like a real light. So, I started to wonder if this was actually a fake light. I ordered another light directly from Amazon (Amazon was the vendor) which I received today and it appears that this new light is genuine. When I stare at the two lights and packaging side-by-side, the differences are EXTREMELY subtle, to the point that I had to wonder if the original light simply had a malfunctioning Ten-tap and that the differences I was seeing were simple manufacturing variance. On the attached photos, the suspected counterfeit light is on the top, and the real light (shipped from Amazon proper) is on the bottom. Here are the additional differences that I have found: 1. The ink used on the real light is a bit thicker than the counterfeit one - the fake one has ink that is slightly translucent and makes it look a bit like a factory second. This is really subtle and difficult to tell unless you have a real/fake side-by-side. 2. The word "TEN-TAP" on the flashlight is the same height and font size as the adjacent word "PROGRAMMABLE". On the fake one the "TEN-TAP" is just slightly more squished and lower height than the adjacent word, as if the aspect ratio were off. 3. The line spacing of the text above and below "Patented" is equal on the real light whereas on the counterfeit light the S/N line is much closer to "Patented" than is the "TEN-TAP" line. Again unnoticeable unless you are aggressively comparing a real and counterfeit light side-by-side. 4. The machining of the knurling on the tailcap is different. On a legitimate light, there is a slight 3D depth to the texture -- the grooves are both wide AND deep enough to catch a fingernail. The fake light has a texture that is smoother and with grooves that are more shallow. 5. The lanyard hole on the real light was smaller than the one on the fake light I received (see pic #2) 6. The overall texture of the light on the fake light had a textured glossiness (but very smooth to the touch) vs. a more textured matte finish on the genuine light (pic #2) 7. On the pocket clip there are two cutout notches flanking the long part of the clip that are oriented parallel to the axis of the light -- they are slightly longer on the real light than the fake light (pic #3) 8. The button/switch action is much smoother and easier to depress with the genuine light 9. FInally, on the packaging, the fake light had a California Prop 65 cancer warning (the real one didn't, surprisingly.) On both packages (real and fake) the cardboard insert had a cutout that showed the flashlight -- the real packaging had a corresponding cutout on the plastic packaging while the fake one had plastic covering the cutout. So, that's it. These are immensely subtle differences and without an actual side-by-side comparison, I think they would be quite difficult to identify in isolation. Good luck out there!