A pair of blue glasses
An small UV lamp with keychain
The main function of the pen
1. You can write any of your secrets and will not be seen by anyone.
2. You can mark your items without destroying the appearance of the object, and you can easily distinguish it from other same items.
3. You can make a short-term tattoo on your face or arm, becoming the focus of disco and pub.
4. Give your friend a gift as a gift and give him (her) an unexpected surprise.