Harnesses are much safer for toy and small breed dogs and we highly recommend them for your dog's comfort and safety. A harness takes a lot less pressure off the throat . Excitable little dogs like Jack Russells tend to pull a lot when being walked and the use of a harness is much more gentle. Not only that, but it is harder for a dog to slip out of a harness while being walked, reducing the chance that it could run away or into traffic.