The innovation of a classic Can a classic product be an innovation? Absolutely yes! Pelikan has managed to combine a fountain pen and a highlighter in one product. The fluorescent yellow ink, specially developed for the Classic DUO Highlighter fountain pen, has been designed to meet the requirements of the technical components of the fountain pen, consequently it was created to be used only with this writing instrument and should not be used. with other fountain pens. Fluorescent yellow ink bottle.