Personally I don't know why I find these so attractive -- their usefulness or their sheer geek value. These GlowRing Safety Markers contain actual radioactive ☢ material Tritium. Tritium has a half life of 12 years. As markers they serve their purpose extremely well. They will glow continously without batteries or an external power source for more than 10 years. Shown above are images at different lighting conditions. I have attached mine to my Nitepalm Field Lamp so that I can find it whenever there is a power outage. I have no complaints. Moreover the thought that these contain radioactive material makes them more valuable -- In the Geek sense I mean. Currently their sale in the US is illegal, so I got mine from the UK where they are bestsellers. Imogometrics gives it a 5 out of 5 Highly Recommended - A Unique Product !. I have a greenish yellow one, but one can choose from 3 colours - Yellow, Red and blue.
FireBox - £9.95
IWOOT - £9.95
Global Military Supplies - £7.99