Material: copper 

Treatment process: diamond 

US size comparison table:

No. 5 (diameter: 15.7 mm, circumference: 49.6 mm) 

No. 6 (diameter: 16.5 mm, circumference: 51.8 mm) 

No. 7 (diameter: 17.3mm, circumference: 54.4mm) 

No. 8 (diameter: 18.1 mm, circumference: 56.5 mm) 

No. 9 (diameter: 18.9 mm, circumference: 59.5 mm) 

No. 10 (diameter: 19.8 mm, circumference: 62.1 mm) 

No. 11 (diameter: 20mm, circumference: 64.6mm) 

No. 12 (diameter: 21.4mm, circumference: 67.2mm) 

No. 13 (diameter: 22.2mm, circumference: 69.7mm) 

No. 14 (diameter: 23.2 mm, circumference: 73 mm)