Our credit card sized Glow card is designed to be an easily carried emergency light source. After just a few minutes of exposure to the sun or another light source, this card will glow for hours. After 30 minutes of exposure, it will glow for nearly 12 hours, making it an excellent emergency light source. This tool does not use batteries and can be reused again and again. The Glow Card is an excellent low cost emergency light that you can take with you anywhere!