Oura Ring 4 smart ring, one of the strongest rings in the market right now. It's smart and eliminates the need for a smartwatch and its uncomfortable look. A ring that is worn and tracks steps, heart rate, health, sleep, anxiety, stress, and many other things from your body. And if you are a girl, it also greatly benefits you in terms of your monthly cycle. Color: Rose Gold Size: 7 Usage duration: Little Regarding the color, it is changeable. You can put a cover on it from Amazon in many colors. For your information, I have a charger that charges all sizes, original.