The Bolt,hex.,6x10 is the lowest priced item on this Transmission schematic.
In this schematic the "Washer,a.spline" is used most often.
Parts such as the Transmission: Gear M-5, Set Ring,20mm, Gear,m-3, Washer,a.spline are included in the Cb250 Nighthawk 1991 (m) Canada / Kph Transmission parts fiche.