Use this kit to size yourself before purchasing an Oura Ring 5. Oura Ring 5 sizes are different from standard ring sizes and Oura Ring 4 sizes Oura Ring 5 is available in sizes 6-13. There are no half sizes A well-fitted ring maximizes data accuracy, comfort, and overall experience Size the exact finger you plan to wear your Oura Ring on. Oura Ring 5 works on all fingers, and you can wear it on either hand. For optimal accuracy, we recommend wearing it on your index, middle, or ring finger Oura Ring 5 should fit securely and comfortably at the base of your finger Your ring should not rotate as you go about normal daily tasks Wear your ring sizer for at least 24 hours to confirm your best fit