Size Before You Buy & NO SubscriptionBefore purchasing the uaue smart ring, we highly recommend referring to the size chart and measuring your finger circumference to determine the most comfortable and suitable size for your finger to avoid the inconvenience of return or exchange. After purchasing the smart ring, you can use the AIZO RING App for free. Monitor your health through the smart rings. Vibration Alert & Friend Function: This smart ring for women has a unique vibration reminder function, which can support reminders for incoming calls, alarm clocks, abnormal health indicators, taking medicine, drinking water, birthdays and schedules, etc. You can set the reminder function you want in the APP 'AIZO RING'. It also includes the function of adding friends, you can also add family and friends to view their health information, making it an ideal gift for friends, couples and family. Sensitive Touch Control: Touch intelligent design, touch pressure-free, easy to use. You can easily a