The Nut,8mm is the lowest priced item on this Starter Motor(fd620de485833∼) schematic.
The Kaf620-maf Mule4010 2010 Usa / 4x4 Starter Motor(fd620de485833∼) consists of twenty-eight pieces with the Starter-electric being the most expensive.
On this parts fiche the Roller is the most specified component.