Please check the 7th image in the left side of the product web page and part,which will teach you how to train dog to accecpt muzzle.Beacuse dogs are anxious about wearing muzzles at the beginning:try to take off muzzles or bite through muzzles. NEW DESIGN: We add head strap design,which will effectively Prevent from taking off by dogs paw. MEASURMENT:Measure circumference of dog'mouth and dog neck.Please check the size map and choose suiable size .Please double check before purchase. HEAD STRAP:If your dogs would never pull off the muzzle by his paw,you can cut the head strap off.Thus you can wear the muzzle more quickly ATTENTION: Our dog muzzle do not suitable for short snout as:Pitbull mix,boxer,dutch mastiff,affenpinscher, boston terrier and so on.