Interesting Spy Activities For Kids：Invisible pens with built-in purple lights. Batteries included and installed. Please Be Careful with small items: Children above 3 years | Write Your Secret Message: These invisible ink pen with purple light will write your secret message. Once your secret message is written with this spy pens, wait a few seconds shine the light from the cover of the pen | Safe for kids:Safety and tasteless ink. Smooth disappearing inks on t-shirts, paper, skin and any surface! Washes easily! Fun for birthday party,treasure hunt,escape room,or classroom activity complete with invisible ink clues | Purple Light Last Long And Ink Will Not Run Out Quickly: The battery of our invisible disappearing ink pen is button cell, it is replaceable. Besides,Ink of this spy pen Will not run out quickly if you use it in normal condition | Great Gift for Boyss Girls: Assorted colors enhance party fun, like Wedding RSVP & Black Light. Perfect for home parties, secret spy & carnival games. Teachers love it for treasure hunts & classroom activities, making learning & play exciting