The Nut,flange,5mm is the cheapest item from this partsfiche.
Parts such as the Taillight: Nut,flange,6mm, Nut,flange,5mm, Unit,tail Light, Plate Center,fend are included in the Cbr600ra 2010 (a) European Direct Sales / Abs Taillight parts fiche.
With two applications this Reflector,fr.refl is the most specified part.