Royal Sovereign 6-Watt Ultraviolet Replacement Bulbs (RSIUVB2PK) UV bulbs are designed for the Royal Sovereign UV Counterfeit Detector and Four-Way Counterfeit Detector Ultraviolet bulbs are used to check for UV-sensitive strips and help identify fake bills and phony IDs Invisible holographic image printed on most government-issued IDs will only be revealed under UV light