The Oura Ring, a sleek fitness and sleep tracker that passes as an unassuming piece of jewelry, is seemingly everywhere. It’s on the fingers of New York Knicks, politicians (when Senator Cory Booker of New Jersey wore it during his recent 25-hour floor speech, it logged several workouts), and a prince. You might also see it on your health-oriented relatives or friends. Maybe you know someone who is using the ring to get pregnant or to track if they’re getting sick (more on that below).The Oura Ring has also been a top pick in our guide to the best sleep trackers since I first tested the Gen3 version in 2023. The newest model, the Oura Ring 4, offers more features, and after six months of testing it, I’ve found that it’s a worthy upgrade.Top pickA stylish wearable with tons of dataOura Ring 4This sleek ring provides highly accurate heart-rate monitoring and solid information on your sleep cycles. But it’s more expensive than many other sleep and fitness trackers, and at times it confuses inactivity with sleep.$399 from Amazon(price varies by color)$349 from Walmart(price varies by color)$349 from Best Buy(price varies by color)The ring’s core features and functions remain the same: It still collects a slew of physiological data, such as heart-rate variability (HRV), blood-oxygen rate, body temperature, and sleep duration. It still uses that data to give you three daily scores, tallying your Sleep score, Activity score, and Readiness score (how recovered and prepared you are for the day based on the previous day’s activity and sleep) in its accompanying app.But the experience is more streamlined and functional, thanks to a handful of new features:Extended battery life: A single charge lasts up to eight days instead of seven.Inclusive ring sizing: The Oura Ring 4 is available in sizes 4 to 15, a wider range than that of the Gen3.Smart sensing: Oura’s new “smart sensing” algorithm makes sure the ring’s sensors are optimized and working to find the best signal through your finger’s unique physiology. It pulls data from the sensor with the best window into your health, rather than burning several LEDs at once.Reproductive health: The upgraded app offers cycle insights and a fertility-window feature (also accessible to Gen3 owners).However, the new ring costs $50 more than the previous generation (depending on the style and finish), and Oura’s app still requires a $6-per-month subscription ($70 for the year if you pay up front) for you to access most of its data and reports; new members get the first month of their subscription for free. And though it’s better at activity tracking than the Gen3, its ability to differentiate rest from sleep isn’t perfect.The Oura Ring 4 is great for new users who want a clear, holistic view of their day-to-day physiology, heart health, and personalized sleep cycles. Its sleeker and more comfortable ring design and more robust and accurate data tracking also make it a worthwhile upgrade from the Gen3.