The ring sizer works like a belt. Simply push the end through the buckle form a ring shape.
Slip the ring sizer onto your finger. Adjust to give a comfortable fit, checking that is just slips back over the knuckle.
When the best fit is achieved, read off the size indicated by the arrow.
TIP: TEMPERATURE IS IMPORTANT. do not measure when your body temperature is either too cold or too hot. a cold finger shrinks while a hot finger expands causing an inaccurate reading.