SIZE NECK SIZE COLLAR WIDTH S 22 - 29cm (8.5 - 11.5") 12mm (.47") M 29 - 40cm (11.5 - 16") 19mm (.75") L 39 - 59cm (15.5 - 23") 25mm (.98") XL 47-71cm (18.5 - 28") 38mm (1.5")