In this schematic the "Nut,flange,6mm" is used most often.
Parts such as the Fuel Tank (1): Nut,flange,6mm, Packing,fuel Fill, Cap Comp,fuel Fil, Clip B8,tube are included in the Gx120k1\wkd6\14zk7403 Fuel Tank (1) parts fiche.
Check out any of the eleven Fuel Tank (1) components enlisted.