We purchased 2 of these in medium for outdoor patios, and our Border Terrier used them the first day.  She is a cautious girl, so we put treats on them to encourage her to get up.  She finished her snack and lay down for a nap!  

Pros: Arrived in 2 days. Good quality. Light-weight and easy to move
Cons: Took 2 people to put the final leg on each one