Parts such as the Taillight: Bulb,tail Light, Packing,seal, Sub Assy Tail Lig, Washer,plain,6mm are included in the Cbr400rr 1989 (k) Japanese Domestic / Nc23-109 Taillight parts fiche.
The Nut,flange,6mm is the cheapest item from this partsfiche.
The Honda TAILLIGHT has eight products enlisted in the schematic.
