Fuel Injector Assembly and Sleeve Insert

A fuel injector assembly for use in an internal combustion engine, and a sleeve insert for such a fuel injector assembly, are disclosed. The injector assembly has first and second components, each component associated with an intended common axis for the injector assembly. A sleeve insert is disposed between the first and second components, the sleeve insert being arranged in contact with at least one of the first and second components to align the at least one component towards the intended common axis.