This fine point marker, is loaded with special ink that is only visible under UV light. It includes a mini UV light, so you can view your messages. Kids love them for writing secret messages and notes to each other, students can highlight text books. You can mark your own 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. Item Name: Invisible Ink Pen Material: ABS Quantity: 4Pcs Color: Random Color Powered by: 3 x Button Cell (Included) Features: with UV Light, Invisible Ink, Gift, Lightweight Length: 13.1cm/5.16"(Approx.) Notes: No color options, the color is sent at random. Due to the light and screen setting difference, the items color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Package Included: 4 x Invisible Ink Pens