Waste of money and time. They require a light source to charge and only last a little while. If your gun is holstered, it is not getting light. If it is in a gun safe it is not getting light. So where will the light source come from to make it glow? If your answer is a flashlight, you need to think about what you are saying.
If you have a light source to charge it, you have enough light to see your target. I see these things marketed to those who want tritium night sights but cannot afford them.