Pen UNO is really thin but the grip section is 3/8" in diameter, similar to a standard pencil, which provides the most comfortable writing experience. Your hand and brain will remember the old days writing with a wood pencil. In addition, the Hi-Tec C Coleto gel ink cartridge is a favorite of many because of its smoothness, reliability, and precision.
"What makes this pen unique is how you retract the tip. Rather than a click mechanism of some sort, the refill stays fixed and stationary in the barrel while the user twists the threaded grip section until the barrel moves its way up and the tip is exposed. Pretty neat!" - The Clicky Post