I inherited a five-year-old 125-pound Labrador retriever who always pulled when he was walked – and his preference was to run. This harness corrected Mac’s pulling within a week. When he pulls, the harness tightens over his opposing shoulder muscle. As it pinches the outside shoulder, it narrows the dog’s stance and forces him to turn back instantly. To relieve that pinch, the dog essentially snaps right into the heel position.
There are other gentle harnesses out there, but with this one, the D-ring is affixed to an additional loop of webbing that extends out from the harness. When you pull on the leash, the loop cinches the harness hard on the side away from the applied force, without letting slack on the inside shoulder.
Mac had been choked with a “pinch collar” his whole life. When I tried that collar, he didn’t stop pulling. Now I take him for walks with a normal collar unless we’re going to be in high-stimulation situations where I might need to control him more.