With four applications this Washer(10x15x1.5) is the most specified part.
Parts such as the Rear Master Cylinder: Washer, O Ring, Piston/cup Set, Boot are included in the Gsxr1100 1987 (h) (e01 E02 4 6 15 16 17 18 21 22 24 25 34 39 53) Rear Master Cylinder parts fiche.