Parts such as the Rear Brake Caliper (3): Washer 6mm, Caliper Sub Assy,, Piston 34x28, Bolt,hex.,6x12 are included in the Cb500 1999 (x) France Rear Brake Caliper (3) parts fiche.
In this schematic the "Bolt,hex.,6x12" is used most often.
The lowest price component in this Rear Brake Caliper (3) parts-list fiche is the O Ring.