A sample from the products for the Rear Caliper (model S/t/v/w) include: Spring, Piston Set, Piston Set, Piston Set.
In this schematic the "Bolt,housing" is used most often.
The most reasonably priced component used on the Gsxr1100w 1993 (p) Usa (e03) Rear Caliper (model S/t/v/w) is the Bolt.