The security pen with uv light features a long life uv pen for invisibly marking items and a built in led uv reader for viewing the security pen is ideal for making a mark that is invisible to the naked eye until the built in uv light or another uv light is used over the area the uv light can also be used to check for watermarks on bank notes and other documents to invisibly mark documents or bank notes or to write secret messages batteries included note this product has been tested f