4 In 1 Design: our invisible ink pen comes with UV light and 3 invisible ink colors, choose the desired colors to write your secret message and turn on the light at the top of the marker to make the message appear Reliable Material: our UV light pens are made of quality ABS plastic shell, not easy to break, tear or fade, providing a smooth and pleasant writing experience, and the ink is odorless and safe to use Portable Size to Take: our invisible pen with UV light measures about 14 cm/ 5.5 inches in total length, light in weight and compact in size, convenient for you to take and store, helps to keep secret and mark your personal belongings like shirts, paper and crafts Easy to Use: our spy pen is simple to use, just choose the desired color, then write or draw as you like, finally turn on the UV light to show the text or image, the message is invisible under normal light, only becomes visible when exposed to UV light Interesting Party Gifts: our secret pen is interesting and funny, ideal to serve as a class prize, gift bag filler, Christmas stocking stuff and party favor, giving your students, kids and guests a big surprise, and bringing fun to your parties