The Oura Ring 4 Smart Ring Activity Tracker in size 5 is a sleek and stylish fitness technology device made from titanium and metal. It features a 240 x 240 display resolution and provides measurements for heart rate, distance, and calories. The ring is powered by batteries and has a battery life of up to 7 days. It is designed for both indoor and outdoor use, and is compatible with iOS and Android operating systems. With features like wireless connectivity, Bluetooth support, and a variety of sensors including SpO2 and GPS, the Oura Ring is an advanced tool for tracking and monitoring your fitness goals.