Actuator which can be actuated electromagnetically includes a coil, a magnetically conductive actuator sleeve being fixed in the magnetic field thereof. The magnetic field passes radially from the actuator sleeve to an axially movable armature and passes axially in the area of a pole plane from the armature to a return member which is stationary with respect to the actuator and, in so doing, generates a magnetic force which displaces the armature. The actuator sleeve for the magnetic flux of the coil has at least two functionally parallel passage areas having different cross sections for receiving the armature which has a conducting profile complementary to the actuator sleeve.