Description Pelikan 4001 Duo Highlighter Yellow fountain pen ink is a bright, fluorescent shade of yellow and comes packaged in a smaller 30ml glass bottle. Highlighter ink is best used over a water-proof or water-resistant ink. Pelikan 4001 ink is made in Germany and is very popular for its consistent performance and gentle formula that is safe both vintage and modern pens. Having trouble deciding between colors? Use our Ink Comparison Tool to quickly and easily view different colors side by side. We offer Free Shipping on all orders over $59 for US customers, and for orders over $250 for our Canadian customers.