Vented refill means the pen won"t leak or explode on airplanes, making it ideal for business travelers. Uni Super ink is specially formulated to become trapped in paper, helping prevent criminal check washing and other document alteration. Quick-drying, acid-free, archival-quality ink is fade- and water-resistant to last over time. Uni-flow system ensures a steady flow of ink for consistent line and color intensity. Tip retracts to prevent accidental markings, protects and prolong pen life, and keep ink from drying out on pen tip. Visible ink supply so you know before you run out.