These Uni-ball One gel pen refills are compatible with Uni-ball One gel pens. The refills come in five colors: Black, Blue, Red, Blue Black, and Orange.
The Uni-ball One applies the newly developed "Uni-ball One" ink. The pigment in "Uni-ball One" ink minimizes the penetration of the ink into the paper fibre. As a result, it develops original colours on paper, showing a darker black than an ordinary black ink pen, and showing more vivid colours than other coloured ink pens.
The barrel design is stylish and simple. It features a metal oval-shaped clip that can be easily clipped on your notebook or pocket. The joint part of the clip matches its ink colors.
According to research by Ritsumeikan University in Japan, it shows that the darker and sharper the letters in black, the easier it is to remember. So, the Uni-ball one gel pen in black ink might become your best tool when studying.