Note: Please check the product section or the video in this product listing (XL-Black), which will teach you how to train your dog to accept the muzzle.Measurements: Measure the circumference of the dog's mouth and dog's neck. Please check the second picture and choose the right size. If you're torn between two sizes, the smaller will fit better. Please check carefully before purchasing.ADJUSTABLE: Different sizes to fit different breeds, so you can find the perfect size for your pup.HIGH QUALITY: Made of durable, high-quality nylon that can withstand everyday use and is comfortable to wear.PREVENT BITES: Great for aggressive and energetic puppies, use during training or on daily walks around.