The Gentle Leader Easy Walk Harness is designed to gently discourage your dog from pulling while walking on a leash. Unlike traditional collars, our harness never causes coughing, gagging, or choking because the chest strap rests low across the breastbone. Its unique front chest leash attachment stops pulling by steering your dog to the side and redirecting his attention towards you. And, its patent pending martingale loop provides extra leverage for easy, relaxed control and prevents harness twisting and gapping. Sizing based on dog's girth size. Large fits girths of 26"-36". Breeds such as Shepherds, Rotties, etc.