This 5‎"‎ fine point marker‎,‎ is loaded with special ink that is only visible under UV light‎.‎It includes a mini LED UV black light with batteries‎,‎ so you can view your messages‎.‎Kids love them for writing secret messages & notes to each other‎,‎ students can highlight text books and still sell the book when they finish their coursework‎.‎You can mark your personal property with your house number and zip code in case of theft‎.‎Push the button to open the UV light for viewing your invisible messages‎.‎Type‎:‎ Ink PenCover Material‎:‎ PlasticRefill Color‎:‎ WhitePen Color‎:‎ PurpleSize‎:‎ 13cm x 1.8cm/5.12‎''‎ x 0.71‎''‎ ‎(‎Approx‎.‎‎)‎Notice‎:‎ The words written by it can‎'‎t be erased‎,‎it doesn‎'‎t have 2 heads‎.‎