Size Before You Buy & NO Subscription FeesBefore purchasing the 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. 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. Comprehensive Health Monitoring: This smart ring health tracker features a high-precision advanced chip that continuously tracks key health metrics such as your activity, sleep, heart rate, HRV, body temperature, body recovery, and menstrual cycle. Through the 'AIZO RING' application, you can view these health indicators at any time and adjust your lifestyle based on daily, weekly or mo