A fuel injector for fuel injection systems of internal combustion engines. The valve includes an electromagnetic actuating element which has a solenoid, a solid core, an external magnetic circuit component, and a movable armature for activating a valve closing member which cooperates with a valve seat surface provided on a valve seat member. The valve has extremely small outer dimensions. By optimizing the dimensions of the electromagnetic circuit, the outer diameter of the external magnetic circuit component in the peripheral area of the solenoid is 10.5 mm