Please refer to the 7th image on the product page for guidance on how to safely and gradually acclimate your dog to wearing a muzzle. Some dogs may initially feel anxious about muzzles and attempt to remove or chew through them. NEW DESIGN: Features an adjustable head strap to help prevent dogs from removing the muzzle with their paws. MEASUREMENT: Measure the circumference of your dog’s snout and neck. Refer to the size chart to select the appropriate size. Please verify measurements before purchasing. HEAD STRAP: If your dog does not attempt to remove the muzzle with its paws, the head strap may be removed for quicker and easier application. ATTENTION: This muzzle is not suitable for brachycephalic (short-snouted) breeds such as Pitbull mixes, Boxers, Dutch Mastiffs, Affenpinschers, and Boston Terriers.