One time I received a new, unused flashlight. I used the 16340 for a long time and the button was always flat, then at one point my 16340 ran out of charge and installed the CR123, the next day the button became convex, possibly due to the gas emitted by the batteries. She couldn't get flat anymore. Now I have received a couple of the same unused ones and in one of them so far I only use 16340 and no changes in the state of the button. Perhaps this is how gas affects neoprene or am I mistaken? It would be nice to conduct more extensive observations, but I don't have enough money yet to buy a bunch of new HDS