We at the Emotional Support Animal Society know how important it is to properly measure your dog for an emotional support vest, take a flexible tape measure and place it around his girth – that is just behind the front legs and around his body, making sure you going underneath him or her at the widest part of its rib cage. Once you measure the dog for the first time, do it again to make sure the size of the ESA vest is the correct one for your dog, especially for a small dog.