Some of Kopflex's competition only offer Carburized or Nitrided gearing. It has been Kopflex's experience that both surface hardening techniques have their place. For high impact applications, such as seen in Hot Mills, Carburized gearing offers the longest life due to its deep case depth. For lower impact mills where speeds play a major factor such as cold mills, Nitrided gearing tends to offer the longest life. Although the case depth of nitrided gearing is less than carburized, the surface hardness is higher and more resistant to wear. In the end, customer preference and experience often leads to the gearing provided.