A hearing aid or hearing aid component for placement in an auditory canal andor in or behind an auricle of a wearer is provided with a biofilm-inhibiting coating. The coil spring is rotated about its longitudinal axis and is moved lengthwise so that its convolutions enter successive perforations of the row of perforations in the stack being held in the guide. The recesses are formed so as to leave substantially unaltered the bending moments of these elements.