The Graf von Faber-Castell inks in the 75 ml bottle are an excellent companion for your new or old fountain pen. They offer a variety colors in a stylish and premium glass bottle. Faber-Castell uses their own formula for each ink using high quality ingredients. The quality of the ink shows itself in the even flow. Faber-Castell claims that the inks are indelible meaning they are smudge-resistant, light-fast and waterproof. They cannot be erased and are resistant to many chemicals and solvents.