The Washer,plain 6mm is the lowest priced item on this Muffler schematic.
Some items from this specific schematic: Muffler Comp.exh, Gasket,ex.pipe (nas), Bolt,flange,8x16, Bolt Flange,6x10.
The sixteen Cn250 Helix 1998 (w) Usa Muffler component parts are all listed in this schematic.