Insight Rollerball Pens feature exclusive uni-flow ink system that regulates a steady flow of waterproof ink to the point for consistent smoothness and color intensity down to the last drop of ink. Ink-o-meter provides visible ink supply so you know before you run out. Uni Super Ink helps prevent check and document fraud. Quick-drying ink is also water-resistant, archival quality and acid-free for documenting and record-keeping. Pens are refillable.