Reed pen

The inkstained cut tips of reed pens
Varying diameters

A reed pen (Greek: κάλαμοι kalamoi; singular κάλαμος kalamos) or bamboo pen (traditional Chinese: 竹筆; simplified Chinese: 竹笔; pinyin: zhú bǐ) is a writing implement made by cutting and shaping a single reed straw or length of bamboo.