The Jetstream EDGE, with the world's smallest ball diameter of 0. 28mm, has been newly added to the popular Uni Jetstream series, which is popular for its smooth writing and quick drying. In recent years, the need for fine print of oil-based ballpoint pens has increased, and Uni has begun planning and developing an ultra-fine ball diameter of 0. 28 mm. The world's first ultra-fine ball diameter in the oil-based ballpoint pen category, 0. 28mm. The drawing line width is thinnner than our gel ink ballpoint pen with the same ball diameter. Uses low-viscosity oil-based ink, "Jetstream Ink", so it has excellent quick-drying properties and can write thick, clear lines smoothly. The body axis is designed to express the thin and sharp image of the 0. 28mm ball diameter drawing line in a stylish manner, and also focus on functional aspects such as stability during writing. As a specialized tool for writing fine print, we focused on the material, design, and usability of each part.