Entrust Pro Counterfeit Money Detector Pen Marker (5-Pack), Dollars, Pesos, Euros, Pounds and other paper bill currencies EASY AND FAST - To use, draw a small mark on a paper bill AMBER line means the currency is genuine. BLACK line and the bill may be counterfeit. Amber markings fade within a few minutes. PROTECT YOURSELF and your business from fraud and counterfeiters looking to scam you with fake currency. RELAX knowing that just one detected bill and this product pays for itself instantly WORKS ON DOLLARS, Pesos, Euros, Yen and other paper based currency. Will not work on plastic/polymer notes.