You could adjust or fold according to your head size, very fit for sport running, hiking, Jogging etc. Colorful and fashionable appearance, choose it and just match your current style. Features: Bluetooth version: V4.2+EDR Bluetooth operating range : up to 10m (free space) Transmission frequency range: 2.4GHz-2.48GHz Supported profiles: A2DP, AVRCP, HSP, HFP Frequency response: 20Hz-20KHz Standby time: up to 100 hours Bluetooth musiccall time: up to 5 hours Fully charged time: about 1-2 hours Op