European collar sizes, 38 to 46. The size menu shows the matching collar in inches: 38 = 15, 39 = 15.5, 40 = 15.75, 41 = 16, 42 = 16.5, 43 = 17, 44 = 17.5, 45 = 17.75, 46 = 18. Take your true dress-shirt collar size. Between sizes? Call 780-431-4293 and we will sort it out.