Overexposure to UV rays can be dangerous. Now monitor the sun's UV intensity with this UV tester keychain! They appear clear/white in indoor and when exposed to sunlight the wristbands color changes to one specific red, yellow, blue, purple and orange. They are used as reminders for people to stay in shade and protect themselves against sun's UV rays and mostly used for skin cancer awareness. It suits for people at all ages. Hand out this great gift with your logo to clients and protect them from the UV ray!