Uni-ball 61234PP Vision Elite BLX Refills, Blue Black Ink, 0.8 mm Bold Point, Pack of 2. Airplane Safe-ink will not explode or leak due to a change in cabin pressure during flights. Exclusive uni-flow ink system regulates a steady flow of waterproof ink to the point for consistent smoothness and color intensity down to the last drop of ink. Features uni Super Ink specially-formulated to become trapped in paper, helping prevent criminal check washing and other document alteration. Archival quality and acid-free ink for documenting and record-keeping.