This set includes 1mm, 2mm, 3mm, and 4.5mm custom cut pens. The Pilot Parallel Pen is a remarkable and durable tool that offers crisp edges, sharp hairlines and a totally reliable, smooth flow of ink for beginners and seasoned lettering artists. In a typical dip or cartridge pen, ink travels through one or more slits in the nib and feeds across the writing edge. Skipping (non-delivery of the ink) can occur, particularly in larger pens. The parallel pen has a totally different construction. Ink flows between two layers of metal lying on top of each other, delivering ink to the entire writing edge without fail. Turn the pen on its corner and the pen writes a .5mm monoline -great for your handwriting, flourishing (till your arm gets tired!), making high contrast thin strokes and pen manipulation. You can also blend colors by touching the writing edge of one pen to a second pen loaded with a complementary color. Each pen comes with a black and red cartridge.