SIZE 6: Diameter 16.56mm
SIZE 7: Diameter 17.2mm
SIZE 8: Diameter 18.2mm
How to measure your ring size?
DIAMETER: Use a ruler to measure the inside diameter of a ring that fits you well.
CIRCUMFERENCE: Measure your finger with a strip of paper or string. Wrap the paper around the base of the intended finger, and then mark where the paper overlaps.