The Screw-washer,4x12 is the lowest priced item on this Rear Brake Mastercylinder (cb600f/f3) schematic.
In this schematic the "Washer,oil Bolt" is used most often.
This part-list fiche shows all the components that make up the Cb600f Hornet 2007 (7) European Direct Sales Rear Brake Mastercylinder (cb600f/f3) .