The Fusiony Bamboo Inkless Pen inkless pen is made of bamboo and has a ruler printed on the barrel (up to 11. 3 cm). This pen does not require ink cartridges or refill. The pen’s graphite tip is designed to leave visible traces as it makes contact with the writing surface. Choosing a pen made of bamboo promotes making more sustainable choices, and encourages the use of renewable materials. Writing length: 1500 metres. Nib size: 0. 5 mm.’