A proportionally acting solenoid with a plastics encapsulation having a fastening flange which is integrally formed thereon and contains shaped elements which permit installation of the solenoid onto the housing by axial pressing in, rotation and rotary latching, the shaped elements, in interaction with metallic springs and shaped elements of the housing, holding the solenoid on a housing axially and against rotation, and the springs being tensioned upon rotation of the housing during the installation, and the seal which seals the radial gap between the solenoid and the housing being coordinated, by means of the configuration thereof, with a small axial installation force.