Parts such as the Fenders: Flap,fender,rr, Nut,lock,5mm, Fender-comp-rear,rr,p, Fender-comp-rear,fr are included in the Z550g6 Gt550 1989 Europe Fg Sp Fenders parts fiche.
On this parts fiche the Washer-plain,5mm is the most specified component.
The most reasonably priced component used on the Z550g6 Gt550 1989 Europe Fg Sp Fenders is the Bolt-upset-wsp.