M12/M14 Conversion Washers
M12/M14 conversion washers - radius wheel, tapered/conical bolt/nut
M12/M14 Conversion Washers for Wheel Bolts
These washers allow you to use 60deg taper or conical wheel bolts/nuts on a wheel designed radius seat fitment.
If you have changed to alloy wheels, its likely they will take a taper/conical bolt, but that original steel wheel under your bonnet will need radius fitment bolts.
Rather than carry a set of spare bolts, it would be easier to pop a set of these into your glovebox should you ever need them.
Sold individually, you will need 4 or 5 for a set depending on your stud-pattern.