On this parts fiche the Bolt,flange 8x45 is the most specified component.
The most reasonably priced component used on the Gl1800 Gold Wing 2008 (8) France / Ab Cmf Nav Rear Brake Caliper is the Bolt,flg.dr 10x32.
The Rear Brake Caliper assembly is constructed from several parts from which the Caliper Sub Assy, is the most expensive.