CALISTOUS Remote Signal Extension Synchronous Display U8 Bluetooth Wrist Smart Watch Wristwatch for Smartphones Android Samsung Black Bluetooth Version: Bluetooth V4.0 Talk Time: about 3 hours Range of Frequency: 2.4GHz spectrum Bluetooth Protocol: A2DP + HFP 1.5 + HS P 1.2 Power Supply: Built-in 230mAh rechargeable battery