These Counterfeit Detection Pens are designed to determine whether US Currency is counterfeit. There are three pens per card that feature a simple and easy to use design, making them accessible to a variety of users. To use, simply make a mark on US Currency with the pen. An amber mark indicates that the currency passes the test, while a dark brown or black mark indicates that the bill is counterfeit. Durable and reliable, these pens have been recommended by financial institutions.