I ordered the small bed for my then 7 lbs who is now a 11 lbs mixed Chihuahua.  This is by far his favourite bed to sleep in.  Since purchasing the bed we got a second puppy who is a small breed dog as well.  He also loves this bed.  Because it is a favourite bed for both dogs we are going to order a second bed as they like to have lots of space while sleeping and need more room than the small bed provides.    Although it is a expensive compared to regular dog beds, it is worth the investment for dogs who love to curl up and be cozy.  We no longer have to worry about our puppy being warm enough and find he sleeps better through the night.