That is just a picture of 4 different sizes. They do look cute stacked like that don't they.
I got the pink one in the small and Little Bit & I both like it but I am a little confused about something. The cover is zippered and listing said it was removable and washable but it has what seems to be permanent tufting so I have no idea how you would get this cover off. The sleeping surface is cream colored so it is reasonable to think that it would need washing at some point.