All Sales Final.  All muzzles do not fit perfectly.  But, this one I've used for many types of dogs.  This video, I am using the medium. 
https://www.youtube.com/watch?v=uObe8YCwQTg&t=660s
 
Keep in mind, I have about 40+ muzzle, all for different sized muzzles, none are perfeclty fitting.  If you get stuck with a muzzle you'll never use and you are NOT a groomer, you can donate to your local dog rescue group, veterinarian, or groomer so it's not a full waste.