Custom-molded earpieces that feed a wireless personal monitor mix to a performer, replacing floor-wedge monitors. Standard at the headliner level: IEMs let performers move around the stage with consistent audio and protect long-term hearing. Each performer's IEMs are paired to a wireless transmitter rack that the monitor engineer drives. Some artists tour their own IEMs and rack; others rely on a venue's house system. IEM molds are made from custom impressions of the performer's ear canal and last years.