ltem description from the seller
US Size Comparison Table
No.5 (diameter: 15.7mm, circumference: 49.6mm)
No.6 (diameter: 16.5mm, circumference: 51.8mm)
No.7 (diameter: 17.3mm, circumference: 54.4mm)
No.8 (diameter: 18.1mm, circumference: 56.5mm)
No.9 (diameter: 18.9mm, circumference: 59.5mm)
No.10 (diameter: 19.8mm, circumference: 62.1mm)
No.11 (diameter: 20mm, circumference: 64.6mm)
No.12 (diameter: 21.4mm, circumference: 67.2mm)