Taking thorough measurements of your dog is essential for choosing the correct harness size. Place four fingers behind the front legs to find where to measure the chest (girth) for harness sizes 0, 1, 2, 3 and 4, three fingers for size Mini-mini and Mini and two fingers to take measurements for sizes Baby 1 and Baby 2. The chest circumference should be measured where the strap is supposed to be located. Choosing the correct size ensures maximum freedom of movement and protects the neck and shoulders.