Size Data: XS - back length:12", neck girth:10",chest girth:16";Small - back length:14", neck girth:12",chest girth:18"; Meidum - back length:16" , neck girth:13",chest girth:21"; Large - back length:18", neck girth:17",chest girth:23". (Due to each dog's body size is different, please measure dog's neck&chest&back size before purchasing and compare the size data to choose the right size to buy, if the dog's size is between the two sizes, it is recommended to choose one size larger) Size Reference: X-Small is suitable for small dogs such as Bichon, Fox Terrier, Jack Russel, Scottie; Small is suitable for Boston Terrier, Cocker, Spaniel, Schnauzer, Westie, Pug and other small dogs; Medium is suitable for Cocker Spaniel, Beagle, French Bulldog, Schnauzer etc, small dogs; L is suitable for Beagle, Corgi Standard, Dachshund, English Bulldog etc, small dogs. Soft Dog Pajamas: This dog pajama uses flannel fabric, which is cozy & fluffy, and the cute paw pattern on the fabric can make the dog look more adroable and charming. Dog warm Pjs clothes is not only comfortable to wear, but also can effectively prevent dog hair from falling on furniture and keep the home clean and tidy. Keep Warm in Cold Weather: Thick flannel dog pajamas can wrap your dog's full body, keeping your dog warm in cold weather, especially new puppies have less fat than adult dogs, which can keep puppies warm through the cold winter.Not only suitable for sleeping at night, but also suitable for parties, daily wear, photo shoots, vacation travel and more. Humanized Dog Pajamas : It is pullover design, easy to put on and take off. The whole edge of the dog clothes are made of elastic edging, so that the dog's body can stretch without restraint and move freely. (Tips: dog clothes support hand washing and machine washing, cleaning is very convenient) X-Small is suitable for small dogs such as Bichon, Fox Terrier, Jack Russel, Scottie; Small is suitable for Boston Terrier, Cocker, Spaniel, Schnauzer, Westie, Pug and other small dogs; Medium is suitable for Cocker Spaniel, Beagle, French Bulldog, Schnauzer etc, small dogs; L is suitable for Beagle, Corgi Standard, Dachshund, English Bulldog etc, small dogs.