I thought I had ordered the large bed. However, a medium bed was delivered to me. My German Shepherd/Lab mix doesn't seem to mind, though. She cuddles up and appears to enjoy the comfort of the orthopedic mattress as she naps. As a RN, I know it is vital to get good restful sleep. She is only 18 months old, so I could imagine how much this style of bed could help a much older dog with arthritic changes. When she wears this one out, I'll be ordering another one!