Parts such as the Rear Brake Master Cylinder 1100: M/c Assy,rear, Piston Set,m/c., Pin,cotter 2.0x15, Hose,master Cyln are included in the St1100 1991 (m) Usa California Rear Brake Master Cylinder 1100 parts fiche.
On this parts fiche the Bolt,flange,6x12 is the most specified component.
The Washer,screw 4x12 is the lowest priced item on this Rear Brake Master Cylinder 1100 schematic.