Uni-Ball One P - 0.5mm. The Uni-ball One series of pens is known for its simple, yet elegant design and impressively dark ink color. The Uni-ball One P (or Uni-ball One Pocket) is a redesign of this fan-favorite gel pen with an emphasis on a better fit in one's hand for a more comfortable writing experience. This model is shorter than the original Uni-ball One, but the body is slightly plumper. This short and stout body lends itself well to longer writing sessions. Moreover, the array of subdued and calming body colors and matte finish make the Uni-ball One P even more pleasant to use.
In February 2020, Uni released the Uni-Ball One, a brand new gel pen that came with the newly developed Uni-Ball One ink, a darker and more vivid gel ink. The Uni-Ball One ink is a pigment based ink with larger particles that are less likely to be fully absorbed below the paper surface, thus creating a more vivid ink color. The ink dries quickly and writes smoothly similar to other Uni-ball gel pens such as the Signo.