Oura Gen 3 review: can smart ring worn by celebs and athletes work for you?

The smooth and light titanium ring comes in various colours and finishes and in two different shapes: one with a plateau on top and a more expensive fully round version as tested. A clear plastic inner layer allows you to see the impressive array of components, sensors and contacts, including three bumps that make contact with the underside of your finger to read heart rate and other metrics.