This pen is very interesting. After you've written, the letters are not visible/transparent. If you use UV/LED light on the cap to shine on it, you will see the words. Kids will love these spy pens. Kids will love using this pen to keep their secret while playing detective spy games. Invisible pen brings you an amazing variety of fun activities, from Surprise birthday parties, to revealing a top secret message to their parents or grandparents. Write your secret message and wait for few seconds. Shine the light from the cover of the pen and REVEAL THE MYSTERY OF THE SECRET MESSAGE. Kids will love using this kind of pen to play detective spy games. It brings an amazing variety of fun activities. From Surprise birthday parties, to reviling a top secret message to their parents or grandparents. Fun, flexible and colorful Magic Bending Pencils with Erasers. These are soft pencils that can be bent into any shape as desired! They are non breakable!! The little ones will enjoy taking these to school. This is the perfect gift parents can buy for their kid’s party, or add it in any surprise gift bag. Teachers can show this to their students for any school activities.