Rollerball Pen's exclusive uni-flow ink system regulates a steady flow of waterproof ink to the point for consistent smoothness & color intensity. Ink-o-meter lets you know when you're about to run out. Acid-free, archival quality Uni Super Ink is ideal for documenting & record-keeping & helps prevent check & document fraud. Ink is quick-drying & water-resistant. Pen is refillable.