Your dog hits the end of the leash and the whole walk becomes a tug of war. A back-clip harness does nothing about that, it gives them something to lean into. This one has a front clip as well, and that changes the mechanics.
Nylon webbing with padded chest and belly panels, six colours, sizes M through XL. Four adjustment points let you fit the chest and girth separately, which matters on deep-chested dogs. Two attachment rings: a steel D-ring on the back for ordinary walking, and a front ring at the chest for training.
How to use the front clip
Attach the leash at the chest rather than the back. When the dog moves ahead of you, the line runs across their shoulders and turns them gently back toward you instead of letting them drive forward. It is not a correction and it does not teach anything on its own. It removes the leverage that makes pulling work, so the training you do actually lands. Most people use the front clip during sessions and the back clip once the dog is walking on a loose leash.
Fitting
Two fingers should slide flat under any strap. Measure the girth just behind the front legs, and size up if you are between sizes.
Part of the Leash Pulling Kit, with the long line, treat pouch and clicker that go with it.