The most advantages of tungsten carbide nibs are toughness and resistance to fracture, which depend on the tungsten powder grain size and amount of cobalt used .higher cobalt binder content results in more ductile die material with lower hardness and wear resistance . these dies are used to draw larger diameter wires with heavy reduction at slower speed without much loss in die life. http://www.natust.com/cutting-tool/cnc-milling-cutter/