Highly minimalist yet deceptively clever, Ensso's Uno Pen is destined to become a design icon. The bulk of the all-aluminum pen is just 5.3mm in diameter, but the grip section is 9.5 mm, offering a writing experience similar to that of a standard wooden pencil. The grip section also doubles as the cap, twisting upward to cover the tip of the Pilot Hi-Tec C Coleto gel ink cartridge.