[Write your secret information] Use these to write your secret information to children the built-in UV lamp on the pen cover to reveal the invisible ink - secret information * Plastic of different colors, note that the ink is the same color [Safe and non-toxic] Invisible ink pen is non-toxic, harmless, tasteless and safe for children -shirts, paper, , and any and vanishing ink on the surface. Permanent washable. Note: Children under 3 years are encouraged to use it under the of their parents [Great gift for the party favorite] This UV pen lamp has 30 pieces, which is suitable for children's gift bag and party bag filler Add happiness to Christmas, birthday and parties [Package for use] The package includes 30 UV of each color with built-in UV lamp. Use at any time after receiving Note: Children under 3 years are encouraged to use it under the of their parents Material: Plastic colour: Mixed colours Package Contents: 30 x invisible ink pen Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.