The AMZMAX R02 Smart Ring Fitness Tracker features four size options, with internal diameters ranging from 18.1mm to 20.6mm and a lightweight design at 4.4g. Powered by the RF03 chipset and equipped with a STK8321 sensor, it offers accurate heart rate, blood oxygen, and blood pressure monitoring. Compatible with Android 5.1+ and iOS 8.0+, it supports Bluetooth 5.0 for efficient connectivity. The 17mAh polymer battery delivers up to 7 days of usage and requires only about an hour to charge. With IP68 waterproof protection and stainless steel construction, this tracker monitors steps, calories, sleep, and multiple workout modes, while supporting remote photo control and extensive multilingual app support.