It is an ultra-thin tip of 0.4 mm. It provides precision and makes the pens perfect for work that requires accuracy, e.g. detailed drawings and precise writing. The tip is made of carbide and should retain its shape and is very durable. The ink is biopolymer gel ink that gives lines in clear colors without spreading.
The pens are really, really nice! On the cap is a jewel-like casing and transparent pen body that makes the ink level visible.