If you have a dog that naturally (or through training) walks very nicely on lead without pulling, a body harness is a great choice for him. However, if you have a dog that pulls strongly, the types of harnesses where the leash attaches on the back are a poor choice. Those actually encourage pulling because they allow your dog to put his full weight into pulling you. A good option is the Gentle Leader harness or similar harnesses, which have the leash clip in the front. What happens with those is, when the dog starts to pull, it turns the dog toward you. While they can still pull to some extent, this helps you in training your dog to walk nicely. No type of harness or collar is ever a substitute for proper training, and everyone’s goal should be to eventually only need a flat collar when the dog is trained to walk nicely without straining. All devices that control, correct, or turn the dog are TRAINING devices, not a permanent solution.