Drug delivery system comprising a housing and expelling means with a first rotational member adapted to rotate relative to the housing corresponding to a set and/or expelled dose and comprising a first force transmitting surface, a second rotational member adapted to rotate relative to the housing corresponding to a set and/or expelled dose and comprising a second force transmit ting surface. At least portions of the first and second force transmitting surfaces are adapted to engage each other during setting and/or expelling of a dose, and the first rotational member including the force transmitting surface is formed from a polymeric material containing magnetic particles, wherein the polymeric material having been magnetized to provide a magnet producing a magnetic spatial field. Hereby a spatial magnetic field is generated which varies corresponding to the rotational movement of the first rotation al member.
