The eighteen Dl650 Vstrom 2004 (k4) Usa (e03) Rear Caliper component parts are all listed in this schematic.
A sample from the products for the Rear Caliper include: Retainer, Cap,bleeder, Insulator, Caliper Assy,rr.
The Rear Caliper assembly is constructed from several parts from which the Caliper Assy,rr is the most expensive.