Helmets for applying a magnetic field to the head of a subject, comprising: a housing comprising a concave surface configured to receive a portion of the head of the subject; a motor coupled to one or more of: a first permanent magnet via a first axle along a first axis of rotation, wherein the first axle drives movement of the first magnet; a second magnet via a second axle along a second axis of rotation wherein the second axle drives movement of the second magnet; and a third magnet via a third axle along the third axis of rotation wherein the third axle drives movement of the third magnet, wherein the axes are parallel; and a fit mechanism comprising a adjuster coupled to the first magnet, wherein movement of the adjustor moves the first magnet independently of the second or the third magnet.