3 Stacking 3-in-1 Invisible Ink Marker & 1 UV LED Flashlight Blue Red Yellow Blacklight Pens

3 Stacking 3-in-1 Invisible Ink Marker & 1 UV LED Flashlight Blue Red Yellow Blacklight Pens The inks do write invisibly. You may want the included UV light on to see what you are doing in more detailed work. Most white paper has bright blue color under UV light, making the blue and yellow pen writings barely visible, but fine if you are only looking to hide your passwords. The red pen writings glow a bright hot pink. See the first picture. As pictured on gray cardboard they will all show up. The best result, as pictured, is on a white surface that doesn't glow at all under UV. Use the included UV light to check for a dark surface for best result. Note that the yellow is a finer point, and the writing looks quite yellow while the ink is still wet, but then quickly fades to a blue-green. The UV light throws some violet light along with the light just in the UV range at a frequency of 395nm. With another light I have a little deeper in the UV range at 365nm, the blue and yellow ink fade just a little, and the red glows a brilliant orange-red in color. Press each pen section tightly closed to avoid drying out the ink.

Works great.