Looking for the right size for your Oura Ring? With an Oura Ring sizing kit, you can easily determine which ring size suits you at home. That's because the sizing of an Oura Ring is different from a regular ring size, so measuring with a regular ring sizer doesn't work/ The sizing kit contains different trial rings to try on. Wear the trial ring for 24 hours to make sure the size is right. The Oura Ring 5 and Oura Ring 4 have different sizing kits, so choose the sizing kit that matches the model you want. You'll receive the € 10 purchase price back as credit when you buy your Oura Ring at Coolblue. This makes the sizing kit free.