carbide pen ball has Advanced production techniques and  international technical level. Hardness>1400-1500, roughness Ra0.063-0.8 micron, Diameter Tolerance <0.001mm, lineation 2000-2500m, wear-out<0.003mm, microspore uniform distribution, writes smoothly, lineation clearing, abrasion proof, long using life ,printing ink wet ability well, carry over more printing ink, lineation clearing ; good handle ,takeing bake superabundant printing ink.  Size from : Diameter 0.38 - 1.4mm .