Okay, first impressions: The ring takes a few minutes to set up. Once you pair it to your smart device via the free Oura app , you're prompted to answer a few questions, such as your height, weight, and current goals. I chose the somewhat broad "Improve my health," but other options include "Be productive and energetic" and "Manage stress levels." From there, you slip the ring onto your finger — any digit is doable, though index, middle, or ring tend to work best, according to the brand — and it will start reading your heart rate and body temperature. By the next day, you'll start receiving three key numbers or "scores," all on a scale of 0 to 100, with 100 being the best. The Sleep Score tells you how well you slept; the Activity Score is based on estimated calories burned throughout the day; and the Readiness Score refers to the extent to which you've recovered from the previous day's activities and how, well, ready you are to take on the day ahead. (In other words, this number indicates "your capacity to perform at your mental, emotional, and physical best," according to the online description.)