The Stylus by Streamlight is a pen flashlight that features a single white, red, blue, green or ultraviolet high-intensity LED powered by three AAAA alkaline batteries. Although the batteries last 20 times longer than many standard flashlight batteries – providing up to 60 continuous hours of light -- eventually the batteries lose charge, and you must open the flashlight to replace them. Opening your Stylus doesn’t require any special tools. Streamlight has designed it with a simple screw-style battery compartment cap.
Rotate the tail cap – the end of your Stylus opposite to the LED end, remove it and set it aside. Upend the flashlight over your hand to slide the old batteries out of the flashlight barrel. Dispose of the old batteries.
Insert the first new battery – positive end pointing into the barrel. Insert the other two batteries in the same way.
Screw the tail cap back onto your stylus. Turn on the light to confirm that it works.