Small: Less than 20 lbs. Sample Breeds: Boston Terrier Chihuahua French Bulldog Maltese Miniature Poodle Miniature Schnauzer Pomeranian Pug Shetland Sheepdog Shih Tzu Yorkshire Terrier Medium: 20 to 50 lbs. Sample Breeds: Airedale Terrier Australian Shepherd Basset Hound Beagle Border Collie Brittany Bulldog Cocker Spaniel English Springer Spaniel Pembroke Welsh Corgi Poodle Siberian Husky Large: 50 lbs. and over Sample Breeds: Boxer Collie Doberman Pinscher Great Dane German Shepherd German Shorthaired Pointer Golden Retriever Labrador Mastiff Rottweiler Saint Bernard Weimaraner