On this parts fiche the Bolt,housing is the most specified component.
This schematic depicts all components used in the Gsf1200sa 2000 (y) (e02 E04 E17 E18 E22 E24 E25 E34) Rear Caliper (gsf1200t/v/w/x/st/sv/sw/sx) partslist.
Of all the components that make up this Rear Caliper (gsf1200t/v/w/x/st/sv/sw/sx) the Bolt has the lowest price.