Pen Uno is a most minimal pen designed to be a pleasure to write with and beautiful to see. With only 5.3mm in diameter it is one of the slimmest pens ever manufactured, yet it is very comfortable to use because its holding barrel is slightly wider. This barrel also serves as a twisting cap that protects the pen tip when not in use. Pen Uno is precision-machined out of space-grade aluminum and anodized in five distinct colors: space grey, silver, gold, rose gold, and red. Pen Uno uses the widely available Hi-Tec-C Coleto gel ink cartridge. This cartridge writes exactly the same as the regular Hi-Tec-C but it is much slimmer in diameter because it was designed for a multi-color pen system. Taking advantage of this super slim cartridge Pen Uno is one of the most minimal pens ever designed.