The lowest price component in this Rear Master Cylinder parts-list fiche is the Pin Cotter,2.0.
Parts such as the Rear Master Cylinder: Piston-comp-brake, Clamp,hose, Cylinder-assy-master,rr, Bolt,6x14 are included in the Rm65 2003 (k3) Usa (e03) Rear Master Cylinder parts fiche.
On this parts fiche the Washer,10.5x15 is the most specified component.