Ruffwear Float Coat sizing is based on the girth measurement of your dog’s ribcage (the widest part of the ribcage behind the dog's front legs). Once you have taken this measurement, please refer to our Sizing Tool, linked under the size drop-down on the Float Coat Page. If your dog's measurement falls between sizes, we recommend choosing the smaller size. Check out our "About: The Float Coat" video for more details. Skip straight to 2:12 for tips on fitting and adjusting the Float Coat.