I bought an x large for my labrador, who loves it. As soon as it came out the bag, she laid in it.  It's just right for her and she can rest her head on the padded edge. She likes to stretch out rather than the enclosed beds. The floor of the bed she lays on has good padding too. The underneath has grips on and doesn't slide on flooring or carpet.  

We love it so much that we have one in the front room for her and one in the kitchen and a medium one for our very large cat! He now spends more time in it than on the bed! It's the first bed he has liked.

They were cheaper at Wayfair too, than the first one (which was the same) that we bought. Ours are cream bottom with chocolate brown lining. They have washed well too. Fabulous bargains!