Bluetooth V4.2 / Profils: A2DP 1.3, AVRCP 1.6, EDR, HSP 1.2, HFP 1.6, TWS / ~10m distanceLoudspeakers: frequency range 20Hz~20kHzBluetooth: frequency band 2.4GHzBluetooth: radiated transmission power max. 2.5mW SNR / THD / Impedance: 95dB / 0.1% / 32Headphones: 2x 50mAh lithium polymer battery 3.7VHeadphones: charging time ~2 hoursHeadphones: talking time ~3 hrs. / playing time ~3.5 hrs.Standby time ~20 hours (BT connection, no music)Charging case: 300mAh lithium polymer battery 3.7VCharging case: charging time ~2.5 hours (DC 5V/1A)Charged charging box charges the headphones ~3 timesOperating temperature: 10 degrees C up to +50 degrees C