Artline BLOX by Shachihata are definitely unique! This plastic (felt-tip style) marker has a 1.0mm tip and oil-based, permanent ink. The outstanding feature of the Artline Blox are the concave and convex patterns on the barrel. This enables you to connect one Artline to another. You can even connect Artlines of different types to each other. For example, you can connect your Artline Permanent Marker to your Artline Mechanical Pencil and Artline Highlighter!