These "glow-in-the-dark" tapes are energized by a new, long-lived photo-luminescent mineral (strontium oxide aluminate) that is non-toxic & non-radioactive. These photoluminescent tapes are 9 mils thick (9/1000") and charge fully with only 5 minutes exposure to light. Any type of light will charge the tape, but sunlight, halogen, xenon, & fluorescent lights work best. They can be recharged nearly an infinite number of times and can last as long as 20 years. These tapes are adhesive with a peel-off backing, so be sure to apply only to clean, dry, oil-free surfaces that are above 50°F. Since the tape is 9 mils thick thinner widths (1/2”) tend to be easier to work with.