Copper washer -DIN7603- 14x20x2mm – used as gasket for spark plug/cylinder head M14 (spark plug type NGK B, Bosch W)

We use these to shim out our sparkplug, to get the open side of the electrode towards the intake for the best possible combustion.

Put a marker on the plug so you can see where the open side is with the plug screwed in.

Then adjust the thickness of the copper washer by sanding on a piece of sanding paper on a flat surface.