Medium size Any small dog up to the size of a STAFFIE will be suitable for the medium Hound Sleeper. Two JACK RUSSELL’S, PUGS, YORKIES etc will fit on one medium size together. Large size BULL TERRIER size up to a BOERBOEL, GOLDEN RETRIEVER, ROTTWEILER, GERMAN SHEPHERD, and LABRADOR dog for the large Hound Sleeper. XLarge size GREAT DANES, ST BERNARD