On this parts fiche the Washer,10.5x15x1.5 is the most specified component.
The Front Master Cylinder (kz1000-a2 assembly is constructed from several parts from which the Cylinder Assy,master is the most expensive.
A sample from the products for the Front Master Cylinder (kz1000-a2 include: Holder-brake,master C, Hose-brake, Cylinder Assy,master, Bolt-hex Head,6x25.