I have the Fuel 3 from S&C, not the Fuel4. I used the device on the strap to open the door in order to put the batteries in. I've heard about how flimsy the doors are so I tried to be gentle. Gentle didn't work because you have to apply a decent amount of force to open it. Tried a little harder and it opened! Too bad the door broke. I had just taken out the headlamp out of the packaging 5 minutes ago! I'd return it, but shipping it back alone would cost about half the price of the headlamp itself. Guess I'll just continually replace the door every time it breaks.