S-Chest 14.9inch, Back Length, 9.8inch, Fit for 4.4-6.6 pounds dog; M-Chest 17.3inch, Back Length, 11.8inch, Fit for 6.6-9.9 pounds dog; L-Chest 19inch, Back Length, 13.8inch, Fit for 9.9-12 pounds dog; XL-Chest 21.5inch, Back Length, 15.8inch, Fit for 12-14 pounds dog; YOU CAN CHECK THE DETAIL SIZE ON PICTURE;