Size:XL XS Size: Neck: 8.3 Inch Chest:12.2 Inch Back: 7.9Inch S Size: Neck:9.4 Inch Chest:14.2 Inch Back:9.8 Inch M Size: Neck:11Inch Chest:16.5Inch Back:11.8Inch L Size: Neck:11.8 Inch Chest:18.1 Inch Back:13.7 Inch XL Size: Neck:13.4Inch Chest:20 Inch Back:15.7 Inch How to measure: Chest:Measure the thickest part of chest .(Usually behind the two legs) Neck:The Girth of Necklace. Body:Make sure your dog is standing properly,not sitting,or laying down. Measure from along the dog’s backbone from the base of the neck to 5 CM front of base of tail.