People that stacked Oura
The ring is easy to wear, the battery lasts for a long time, and the app displays the results of the tracking in a very clear and intuitive way. The trends view is what makes the real difference: observing the changes in one's wellbeing over time is powerful
The best wearable I've used for sleep tracking, but sizing is super important (even slightly too large and it will slip off during the night). Get their sizing kit before ordering. Only caveat, it's useless during the day.