Some say you make your own luck. I say get one anyway. Just to be safe. RING - INSIDE DIAMETER (MM) USA/ CANADA UNITED KINGDOM/ AUSTRALIA EUROPE GERMAN/ RUSSIA/ ASIA INDIA/ CHINA/ JAPAN NETHERLANDS/ SWITZERLAND 16.5 6 M 52 16 1/2 12 11 1/2 17.4 7 O 54 17 1/4 14 14 18.2 8 Q 57 18 16 16 1/2 18.9 9 R 1/2 59 19 18 19 19.8 10 T 1/2 62 20 20 21 1/2 20.65 11 V 1/2 64 20 3/4 23 24 21.5 12 Y 67 21 1/4 25 26 1/2
