Oura ring gen 3 and 4 sizing kit To get your size, wear the ring for a few days, as your fingers swell and change throughout the day/night depending on activity, hydration, etc. If possible, opt for a size you can wear on two different fingers of either hand, so you can switch to the other finger if needed. Optimal placement is on the index or middle finger, according to Oura, but I’ve had good luck on my ring finger too. Add it to a bundle so I can discount shipping for you!