Fude Pen Hoso-Taku, also known as Brush Pen No. 7, is a single-sided water-based dye. With a flexible felt tip, it can be used to create thick or thin lines with ease and works well with any writing style. Allows for great consistent lines and a dark black ink color. Refill cartridge is interchangeable with the Kuretake Brush Pen No. 8 cartridge.