I got the large even though my buddy is medium sized because he's one of those dogs that likes to stretch all of the way out plus he likes to spin and nest.  I looked at dog beds in stores that just didn't feel like they had enough fill.  Looked online and found dog beds that would fit what I wanted but they were very expensive.  I found this one on Wayfair, read the reviews and decided to give it a try.  Not only is this one as described, the price was right.  There's lots of room on this very fluffy well made dog bed for him.  In fact, he's so enthralled with it that he's stopped getting on the couch.  He's happy, so I'm happy!