It writes with invisible ink made of special high-brightness ultraviolet visible compounds 

This means the ink is completely invisible under normal light 

Near the visible spectrum of light. Flip the pen over, shine the light on the spot where the ink was used and your hidden message will be illuminated

You can use it in various and amusing occasions: secret messages, invisible tattoos, fantastic drawing in the darkness, personalized objects, highlighter and anti-counterfeiting etc.

Package includes 6 * LR41 button batteries