Kuretake Ink Cartridge Refill (for Cartoonist Brush Pen No. 22)
These cartridges fit the Kuretake Brush Pen no. 22 (also known as the Cartoonist "Chuji" Fude Pen) -- the refill cartridge screws onto the brush tip and replaces the entire pen body. Available in black or white.
This water-based pigment is permanent, lightfast, waterproof, and smudge-proof when dry.