UK size O = US size 7 = European size 54 = approx 17.35mm inside diameter UK size Q = US size 8 = European size 57 = approx 18.19mm inside diameter UK size R 3/4 = US size 9 = European size 60 = approx 18.89mm inside diameter UK size T 1/2 = US size 10 = European size 62 = approx 19.84mm inside diameter UK size V 1/2 = US size 11 = European size 65 = approx 20.68mm inside diameter UK size Y = US size 12 = European size 67 = approx 21.49mm inside diameter
