Stainless steel is hypoallergenic with high resistance to rust, corrosion and tarnishing. Basic maintenance is required. Stainless steel is hypoallergenic with high resistance to rust, corrosion and tarnishing. Basic maintenance is required. Both the size and design are easy to match anyone. To avoid the inappropriate size, please refer to the listing before placing your order. [Size] Japan 9 = US 5 (diameter about 15.7mm) Japan 12 = US 6 (diameter about 16.5mm) Japan 14 = US 7 (diameter about 17.3mm) Japan 16 = US 8 (diameter of about 18.1mm) Japan 18 = US 9 (diameter about 18.9mm) US 11 No. (Diameter approx. 0.8 inches (20.6 mm)); Japan 25 = US 12 (Diameter approx. 0.8 inches (21.4 mm)).