A breakthrough in calligraphy pen design, these pens feature a nib that consists of two parallel plates, allowing the writer to produce lines sharper than existing calligraphy pens. Ink cartridges can be switched in the pen to create gradated colour lines and mixed colours. This set contains 4 pens with different size nibs (1.5mm, 2.4mm, 3.8mm and 6.0mm). each pen comes with 2 ink cartridges [black and Red]. these calligraphy pens are refillable. Additional parallel pen ink cartridges are sold separately.