Dri Mark Products Tri-Test Ultraviolet Counterfeit Detection System, Black (351TRI) Compact and Portable-Operates on 3 "C" batteries or optional AC adapter (best with Polaroid C batteries) Maximum Protection Against Counterfeiting and Fraud. Detects Washed Bills with Powerful UV LED light to reveal UV Security Strip on US currency 5 Dollars and larger. Counterfeit Detection Pen Tests for genuine US Currency Paper-White LED backlights Watermarks and Micro Printing Reveals UV Security Markings on Drivers Licenses, Credit Cards, Passports, International Currencies, Cashier's Checks, Money Orders and more Powerful LED's last for years Caution: Do not look directly into or stare at the UV lights. Prolonged exposure can cause eye damage. Keep this unit away from children. When operating your Tri Test Detector, be sure to turn off the unit after each use. Leaving the UV lamps on for long periods of time can weaken performance and cause false test results.