The Gentle Leader Headcollar A BREAKTHROUGH IN DOG TRAINING QUICKLY ENDS FRUSTRATING BEHAVIOR ON THE LEASH. This NOT a Muzzle. When fitted properly, your dog is free to open his mouth to eat, drink, pant, fetch, bark and even bite - except when you close his mouth by pulling on the leash. The Gentle Leader Headcollar quickly controls jumping, pulling, barking, chewing and begging. It even teaches sit and stay in one easy lesson! You will be amazed at the results and how well you dog behaves on your first walk with the Gentle Leader.