The Screw,washer,5x20 is the lowest priced item on this Steering Stem / Horn schematic.
A sample from the products for the Steering Stem / Horn include: Bolt,flange,10x35, Bolt,flange,6x25, R/brg Tap N/com, Washer,plain,20mm.
With all the components that make up the CB750L LIMITED 1979 (Z) USA STEERING STEM / HORN assembly. The Washer,plain,20mm is the most frequently specified with two applications.