The Nut,square,5mm is the lowest priced item on this Cylinder Head schematic.
Parts such as the Cylinder Head: Bolt,flange 6x48, Nut,square,5mm, Spark Plug (nd), Guide,valve (oute are included in the Cb1300 2008 (8) Singapore Cylinder Head parts fiche.
The most expensive part in this assembly is the Head Assy,cylinde.