Gel ink combines the durability of a ballpoint with the smooth nature of a roller-tipped instrument. Features acid-free, water-resistant and fade-resistant ink for thick, vibrant writing. uni-ball® ensures premium quality performance with every refill. Refill Format: Standard Gel; Refill For Series: uni-ball® Gel IMPACT™ Pens; Refill Ink Color: Black; Color Family: Black.