Fuel injector nozzle

The injector (1) has a section (5) rotatably and directly or indirectly guided in a recess (14) at a cylindrical head (2) under an intermediate arrangement of a mounting socket (3). The section is locked in an inserted position by a driving device (6) at the cylindrical head, and includes an outer contour (10) that allows an assembly of the injector at the cylindrical head in a defined relative position. The recess includes a polygon-like inner contour (12) that is adapted to the outer contour of the injector. Independent claims are also included for the following: (1) a cylinder head of an internal combustion engine (2) a mounting sleeve for indirect mounting a fuel injector on a cylinder head.