This 0.2mm thick petcock indexing washer allows you to fine tune the tightened stopping point for proper petcock alignment on V700, Ambassador, 1969-1971 V750 Special, 850GT and Eldorado fuel tanks. Allows you to choose the angle at which your petcock lever swings, prevents the need to stack multiple gaskets and over or under tighten the petcock against the fuel tank. One of these shims will stop the petcock 72 degrees or one fifth of a turn from where it would have stopped with no shim installed. A few of these on hand and you'll be set no matter what thickness your sealing washers are. The sealing washer to use in conjuction with these is 90714123, available separately.