On this parts fiche the Nut,hex.,8mm is the most specified component.
A sample from the products for the F-13 Front Wheel include: Bolt,flange,8x100, Retainer Fr Wheel, Valve,rim(bs), Valve,rim(dunlop).
The component with the lowest price in the F-13 FRONT WHEEL schematic is the Screw,cross 5x20.