The webbing on the harness is one single piece so the harness is very adjustable to different proportions. We recommend selecting a size based on the weight of your dog. Please size up if your dog is on the edge of the weight range.
Small: 10-25 pounds (5-11kg)
Medium: 25-50 pounds (11-23kg)
Large: 50-75 pounds (23-34kg)
X-Large: 75-108 pounds (34-48.9 kg)