SIZING
A smart ring only reads accurately when it sits flush against the skin. Measure at home with paper and a ruler, then confirm with the free sizing kit that ships with every order — no risk, no extra cost.
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TK BIOSYNC · FIT GUIDE
How to measure
- 01
Wrap a strip of paper
Cut a thin strip of paper and wrap it snugly around the base of your index finger, tight enough that it doesn't slide over your knuckle.
- 02
Mark
Mark where the ends of the paper meet.
- 03
Measure
Lay the marked paper flat against a ruler and measure the length in millimeters. This measurement is your circumference.
- 04
Match the chart
Find the closest circumference in the size chart below. If you fall between two sizes, choose the larger size for a more comfortable fit.
Size chart
| Size | Inner Ø | Circumference |
|---|---|---|
| 6 | 16.5 mm | 51.9 mm |
| 7 | 17.3 mm | 54.4 mm |
| 8 | 18.1 mm | 56.9 mm |
| 9 | 18.9 mm | 59.5 mm |
| 10 | 19.8 mm | 62.1 mm |
| 11 | 20.6 mm | 64.6 mm |
| 12 | 21.4 mm | 67.2 mm |
| 13 | 22.2 mm | 69.7 mm |
For the most accurate fit, measure at the end of the day. Avoid measuring when your hands are cold, as finger size can change slightly.
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