On this parts fiche the O Ring,10mm is the most specified component.
The seventeen Kaf620-m9f Mule4010 2009 Usa / 4x4 Gear Change Mechanism component parts are all listed in this schematic.
The most reasonably priced component used on the Kaf620-m9f Mule4010 2009 Usa / 4x4 Gear Change Mechanism is the Ball-steel,13/32.