I highly recommend that you don't attach a leash to your Shih Tzu's collar. The collar should hold identification tags but shouldn't be used for walking. Please purchase a harness for activities that require a leash instead. The Shih Tzu is a brachycephalic breed. Any pressure on the windpipe or trachea can cause the trachea to permanently collapse. Using a dog harness will help prevent this type of injury from taking place.