The bosch common rail (CR) hexagonal coil adjustment shim is a critical adjustment component with a hexagonal geometry that operates precisely under high pressure and contributes to maintaining stable injection pressure in diesel injectors. It plays a direct 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 ensure high surface quality, superior wear resistance, and high measurement precision, it is manufactured with high accuracy using a lapping process.