A couple of nights ago I was using my Sure Fire G6 light which worked perfect. I turned it back on about 1 min later and it did not work. I figured the bulb went. Later when I installed a new bulb it still would not work only to find out when the batteries go they don't start to dim but just shuts off. Needless to say I learned something new about modern flashlights. Hope this helps someone in the future and saves them a trip for a new bulb and $30.00. (High intensity)