The Wellue O2 Ring is a medical-grade pulse oximeter heart rate monitor designed for sleep apnea testing. With a quick charge time of 2-3 hours and a power source of rechargeable batteries, this compact device is easy to use. The pulse oximeter without probe measures oxygen levels, pulse rate, and motion with built-in memory for up to 4 sessions, each lasting up to 10 hours. The sleek black O2 Ring is lightweight at 0.53 oz and has a form factor of a finger ring, making it convenient for continuous monitoring. The OLED display shows real-time data for accurate analysis, and it comes with a 1-year manufacturer warranty.