Of all the components that make up this Seat Tail Cover (model D) the Washer has the lowest price.
Parts such as the Seat Tail Cover (model D): Lock Washer, Screw, Washer, Cushion are included in the Gsx250s 1982 (z) General Export (e01) Seat Tail Cover (model D) parts fiche.
In this schematic the "Washer" is used most often.