AKG WMS40 Pro FLEXX Presenter Set ISM - diversity wireless system with three switchable frequencies (863.100, 864.375 and 864.850MHz), 1x PT 40 Pro pocket transmitter (works with one AA battery for up to 30 hours), SR 40 Pro FLEXX diversity receiver in metal housing, 1x AKG CK 55 L lavalier microphone with cardioid polar pattern, frequency response: 150Hz-18kHz, cable length: 160cm, includes batteries and power supply. Available in 3 different frequency groups.