X-mini KAI X3 Bass port with 66mm driver for enhanced bass and audio quality Input connectivity - microSD card reader and Bluetooth Built-in microphone Up to 8 hours of play time True wireless stereo audio performance when paired with another X-mini Kai X3 Operating frequency range: 2.4GHz – 2.48GHz Wireless range: Up to 10 metres (33 feet) Bluetooth compliant: v4.0 Bluetooth profile support: A2DP, AVRCP, HFP, HSP Bluetooth playback time: Up to 8 hours