Mobile Phone BT Connection Smart Ring Health Tracker Rechargeable Waterproof Smart Ring for Men Women Black No. 20 Item Type: Smart Ring Material: Aluminum Alloy, Ceramic, Electronic Components Battery Type: Lithium Battery (Shipped With Built In Battery) Battery Quantity: 18mAh Duration: 3-5 Days Charging Time: 45 Minutes Protection Grade: IPX8 Suitable size: Ring Number: 17, Finger Circumference: 52.12mm, International Code/US Code: 5.5/6/6.5, Inner Diameter: 17MM Ring Number: 18, Finger Circumference: 55.26mm, International Code/US Code: 7/7.5, Inner Diameter: 18MM Ring Number: 19, Finger Circumference: 58.4mm, International Code/US Code: 8/8.5, Inner Diameter: 19MM Ring Number: 20, Finger Circumference: 61.54mm, International Code/US Code: 9/9.5/10, Inner Diameter: 20MM Ring Number: 21, Finger Circumference: 64.68mm, International Code/US Code: 11/11.5, Inner Diameter: 21MM Ring Number: 22, Finger Circumference: 67.82mm, International Code/US Code: 12/12.5, Inner Diameter: 22MM