Please note that if your dog has not worn shoes before, it may take some time to get use to. Encourage them to move around and feel more comfortable with wearing shoes. Your dog should always be supervised and should not be left unattended when wearing shoes. And, do not leave shoes on your dog for more than 5 hours as the heat may cause discomfort and irritation to your dog.
In order to get better fit for your dog, you may want to check below detailed measurement for the different shoe sizes.