Vertical bevel housings were originally fitted with 'Reduced width' plain 5/16" washers - so they did not foul the bevel housings.
Update May 2022: Because of the difficulty obtaining these washers, we have been recommending people to use Item 0102 (our reduced width spring washers) for the last 3 years, when fitting to the SOHC Vertical Bevel studs . . . and actually they look just the same when fitted, however, our specialist washer supplier has managed to provide us with one more batch of the correct 'reduced width' plain washers shown here .. . I suspect this will be the last time we are able to obtain them.
These are also for other applications where 5/16" fastenings are used, but you dont want a wide washer fouling confined areas