I have purchased the Ultrahuman Ring Air as an alternative to the Oura Ring 4. Ultrahuman doesn't require a monthly subscription for the wearer to get health reviews (while Oura has a monthly fee of $6). The ring is lightweight and looks well made. The size is right and fits well (I highly suggest that buyers will purchase the ring sizer first). The ring doesn't interfere with my normal routines and hardly noticeable. It tracks sleep and my activities very well. The battery is decent. The app is excellent. It gives very helpful insights and suggestions for health improvements. It has video and audio to help with breathing, workout, sleep, etc. The ring and app have personally encouraged me to make better health choices. Overall, I'm very happy with my purchase.