Please check the size chart carefully before you decide
S (back length: 24 cm / 9.45 inches, chest: 33 cm / 12.99 inches, neck: 27 cm / 10.63 inches) is suitable for 1.5 - 2.0 kg
M (back length: 29 cm / 11.42 inches, chest: 40 cm / 15.75 inches, neck: 31 cm / 12.2 inches). It is suitable for 2.0 - 3.5 kg
L (back length: 32 cm / 12.6 inches, chest: 46 cm / 18.11 inches, neck: 32 cm / 12.6 inches) is suitable for 3.5 - 5 kg
XL (back length 37 cm / 14.57 inches, chest: 47 cm / 18.50 inches, neck: 38 cm / 14.96 inches) is suitable for 5 - 7 kg
XXL (Shoulder: 42 cm / 16.54 inches, chest: 52 cm / 20.47 inches, neck: 40 cm / 15.75 inches) is suitable for 7 - 9 kg
XXXL (back: 51 cm / 20.08 inches, chest: 58 cm / 22.83 inches, neck: 47 cm / 18.5 inches) is suitable for 9 - 19 kg
4XL (back length: 53 cm / 20.87 inches, chest: 60 cm / 23.62 inches, neck: 48 cm / 18.9 inches) is suitable for 19 - 24 kg
5XL (back length: 63 cm / 24.8 inches, chest: 70 cm / 27.56 inches, neck: 51 cm / 20.08 inches) is suitable for 24 - 30 kg