Keep it away from water
I own two of these and they are sub par. There it's no way to lock out the light, so the batteries always stay connected and if you're using rechargeable batteries they'll drain within a day or two depending on the mah of the batteries. Though this is an inconvenience, it's somewhat tolerable. However, what isn't is the fact that they are not in fact ipx8 water resistant. I would even say they fail to meet ipx4 standards. I used these to fish at night in the river in my back yard. They were submersed no more than 24 inches and for no period over 5 minuted continuously. Yet after an hour of fishing, my light began to malfunction. The side button for mode selection would only work intermittently. And the tailcap switch would fail to turn the light off. It switched the mode to strobe. The only way to turn it off was to remove and reinstall the tailcap. Also, if the light is off, and you shake it, it will flicker off and on until you stop shaking it. Even very light subtle shake and movement. These problems were repetitive , and fairly consistent. I sent it back to olight for repair. Approx 6 weeks later my same light was returned to me supposedly repaired. Yet the light still had all the same problems. I contacted olight customer service and this was their response, verbatim:"Ok they were most likely unable to fix it because that light has been discontinued for years and we have not had parts for it for a long time. Sometimes they can fix the M20 but sometimes they can’t. It was technically not under warranty but we tried to fix it anyways. Thanks"Yet these are still being sold, so how it's the warranty up before you even buy them? I know from experience that olight has the worst customer service in the flashlight industry. I own many lights from surefire to cheap bushnell lights from Wal-Mart. Both of which far surpass olight in customer service. Moral of the story, life happens, technology fails, things break ( mostly things are falsly advertised, i.e. ipx water resistant ratings.) so buy from a company with great customer service. It doesn't have to be a $600 light from surefire either. You're better off with a $20 light from Wal-Mart than anything from olight. And that's coming from a former olight fan who owns 6 lights from them.