These UV Fluorescent Marking Pens are ideal for marking money, radios, plastic baggies or paper items to trace them, without visibly marking the item. They will write on most plastics, metals, woods and papers. You can write your name, initials, case number, agency code, date or other information that will fit on the object to identify specific items. Use it to mark paper currency in drug buys. Mark plastic baggies of narcotics or radios, television sets and weapons used in sting operations. It works like a felt-tip pen and dries almost instantly. The resultant marks are invisible to the naked eye and can only be viewed under ultraviolet light.