We have a micro mini labradoodle who is only about 14-15lbs. I ordered her a SM, but just ordered another one in a MD, so I can compare. The SM seems a tad tight due to her ears. The hat is really cute and she will look very sporty with her hat and her Waxed dog jacket ( which we highly recommend) walking around town. It will be nice, when the weather is nasty, to keep her head as dry as possible. Thx for another great product. I'll be anxious to recieve the MD and compare, so we can get to strutting around town.