COPIC Multiliner Brush Set - Primary Brush Four Pack - COPIC Multiliner Brush Pen- The COPIC Multiliner pen is the ultimate drawing pen. The ink is waterproof and COPIC marker proof; so you can do drawings using these pens and then color them in with watercolors or COPIC markers. The pen knibs are replaceable, and there are replacement ink cartridges. The Multiliner Brush Pen has a very flexible brush shaped fiber tip. This tip acts like a Sumi brush; allowing you to draw with lines that are thick or thin- just like painting with a fine brush. Each pen includes the pen barrel itself, one knib, and one ink cartridge. Pigmented ink (not dye). This convenient set comes with one pen each in Red, Yellow, Sky Blue, and Olive Green. Includes a sturdy snap-closed plastic case.