Features: The R18 small rings with Charging Case integrates advanced health monitoring features including heart rate trackings , sleep analysis, and step counting, pair with a portable charging dock for uninterrupted fitness and wellness management. Crafted with epoxy resin, steel, and enamel coating, this strong small rings utilizes sensors for immediate health data and includes a small charging case that ensures extended usage during workouts or daily routines. designs for fitness enthusiasts, health awake professionals, and sleep quality , this small rings offers cautious wear while delivering comprehensive activity and personalizes health insight . Track your performances at the gym, monitors stress levels during work hours, and analyze sleep pattern at homes – all through this multifunction health monitoring rings that syncs seamlessly with your dynamic lifestyle. Combining ergonomic comfort with small wearable technology, the R18 fitness trackers rings features a scratch resistant enamel surfaces and 10 day battery via its charging case, perfect for travel and outdoor adventurers prioritizing health optimization. Specifications: Material: resin+steel No.6: Inner diameter: 16.5mm, circumference: 51.8mm No.8: Inner diameter: 18.1mm, perimeters: 56.9mm No.10: Inner diameter: 19.8mm, circumference: 62.1mm No.12: Inner diameter: 21.4mm, perimeters: 67.2mm Package Includes: 1xSmart rings note: 1.Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. 2.Due to the differences between different monitors, the picture may not reflect the actual colorful of the item.