The bosch common rail (CR) adjustment shim is one of the most commonly used critical adjustment components in diesel injectors, operating precisely under high pressure and contributing to the stability of injection pressure. It plays an active role in the precise control of the amount of fuel injected by the injector. It is a standard component in almost all Bosch diesel injectors. To achieve high surface quality, superior wear resistance, and high measurement precision, it is manufactured with high accuracy using a lapping process.