Christmas Gift | Dazzling Toys Invisible Ink Pen Built in UV Light Pack of 8 Magic Marker Spy Pen 8 per pack Invisible Ink Pens. Grand party favor or gift. Each pen measures: 5 " L. and they come in 4 nice colors: Yellow, Blue, Purple and Pink. Write invisibly secret messages, security markings etc. and only when you shine the light on the message you will reveal the secret behind... A quality product manufactured by Dazzling Toys.