Our Opticz brand UV blacklight reactive invisible ink markers use high quality invisible ink. Perfect for identification marking, wall decoration, and other stealthy security uses. Safe for skin too! Glows an incredibly bright in blacklight! Perfect for metal, glass, plastics, paper. Totally invisible, won't wash off easily, and is only visible under blacklight. These are the markers you want for for invisible, "only visible in blacklight" marking. These markers can be used for: Glow parties, event tickets, industrial coding, security printing, coupons, raffle tickets, inventory control, advertising, and more! Can also be used on: Aluminum, ABS, Acrylic, Rubber, Cellulose, Acetate, Formica, Nylon, Polystyrene, and Polyethylene. Fine tip for precision application. Ink is non-toxic, fast-drying and non-transferable. Prolonged exposure to sun light or continuous high powered UV exposure may cause fading over time.