Collar size: 15 inches (38 cm) 20 inches (51 cm) 16 inches (40 cm) 17 inches (43 cm) 18 inches (46 cm) 20 inches (50 cm) 21 inches (54 cm) 22 inches (55 cm) 22 inches (56 cm) 23 inches (59 cm) 24 inches (60 cm) 24 inches (61 cm) 25 inches (63 cm) 26 inches (65 cm) 26 inches (66 cm) 26 inches (67 cm) 28 inches (71 cm) 28 inches (72 cm) 30 inches (76 cm) 31 inches (80 cm)