Wireless bluetooth smart hand ring Vibration Anti-lost Alarm Bluetooth Mobile-White Bluetooth bracelet with caller's namer and number display when there is incoming calls Compatible with all Bluetooth-enabled mobiles: Bluetooth Version:2.1; Bluetooth Frequency of 2.4GHz Built-in rechargeble battery, energy-saving and nominal charging time is 1 hour Automatic pairing, no need to operate repeatedly. Note: The size of this bluetooth bracelet only fits for women's wrists, it is small for a man to wear it