I bough the size small (25 x 18) primarily for my 20 pound cat. He had a smaller bed that he seemed a little squished in. He fits well in this one & with the old & new bed placed side by side is choosing the new larger bed. 

The bed is shipped squished into a small square box, but it does pop up into shape upon opening. 

The cover will easily zip off for washing similar to other pet beds. 

Photos attached for pet size reference. The orange cat is 20 pounds. The grey cat is 10.