XF special contact lenses was manufactured for the invisible ink, it can see the marked cards which can not be seen by naked eyes. XF contact lenses are manufactured for the marked cards specially, you can see the invisible ink freely which can not be seen by naked eyes.It owns the best quality and your eyes will not easily feel dry when you wear it for a long time.Its Optional Accessories are perspective poker card or perspective poker Maj hong Tips for using the perspective invisible glasses: 1. The best suitable situation is under the white light, especially the energy-saving light. 2. Please make sure to wash your hands clearly before wear the perspective invisible glasses in case of infecting your eyes. 3. Before playing the poker games with perspective invisible glasses, the user who is not a myopia had better wear the glasses about several hours for adapting