I have 3 of these little lights and like them a bunch for rural living and low light pest spotting. They are not good tactical lights. For starters there isn't anyway to use a remote switch which limits them to guns that don't kick, I'd hate to have my thumb on the button when a 12ga. 00 round went off. Other problems with the button are if you screw it in to keep the light on it wants to work its' way out of the cap and if the cap is backed off too much it won't fully engage the battery and gives a dim light. An o ring is the fix for keeping the button in when you want the light to stay on, but to me this makes this neat little lights hobby horses and not serious weapon lights. I have not replaced a battery in the 4 to 5 years that I've owned them and the chargers make it handy to charge in the house or car.