Abstract: A multipole unit normally consists of a support tube, a threaded ring, a plurality of magnetic rings, a plurality of spacer rings and a spring ring. According to the present invention, the structural design of a multipole unit is simplified in that the threaded ring is modified in such a way that the spring ring becomes superfluous. In order to achieve this the threaded ring or a stop arranged on the support tube is provided with spring elements which fulfil the function of the conventional spring ring.