A washing solution for solid-phase immunometric methods which contains stabilizers for the labeling system, and the use thereof. The headset comprises a mounting member for mounting and holding the headset on the head of a wearer, at least a first speaker, and means for connecting the speaker to the mounting member for holding the speaker adjacent an ear of the wearer. The cover portion surrounds an axis and seals against the dash panel. A pick-up horn may further include a serpentine coolant path disposed within the metal body between an outer surface of the at least one outer metal wall and the at least one high-power absorbing load.