When you're on a secret mission, secret messages are key, and that's why you need the Message Dart refill! You can write secret messages with the special pen on the 8 Message Darts, and conceal them until it's time to reveal them. Then you can erase the messages and write new ones! Without the double decoder, nobody will be able to guess your secrets! Nerf and all related characters are trademarks of Hasbro.