The Washer,plain, 6mm is the lowest priced item on this Left Crankcase Cover - Spark Advancer schematic.
This LEFT CRANKCASE COVER - SPARK ADVANCER assembly utilises six Bolt,flange,6x32(s) - the highest specified component.
Some items from this specific schematic: Bolt,hex 6x12, Bolt,flange,6x40, Gskt,point Cover (nas), Gskt,l Side Cover (mca).