The most reasonably priced component used on the Zx550a5 Gpz550 1988 Europe Fg Gr Rear Brake is the Cap-breather.
The Rear Brake is made up of components including this Caliper-assy,rr which is the most expensive.
sixteen components are shown in this Zx550a5 Gpz550 1988 Europe Fg Gr Rear Brake exploded diagram.