Size:L Size Details Size XS: Neck 5.9-7.9inch; chest 8.3-11inch, fit for weight under 3.3lbs Size S: Neck 7.9-9.8inch; chest 11-15inch, fit for weight under 7.7lbs Size M: Neck 9.8-11.8inch; chest 15-17.7inch, fit for weight under 11lbs Size L: Neck 11-13inch; chest 17.7-19.7inch, fit for weight under 16.5lbs Size XL: Neck 12.2-15inch; chest 20.5-22.4inch, fit for weight under 24.3lbs