Ruff Stuff Sizing Guide:
 
The adjustable length shown is the measurement around the collar to the first hole and to the last hole of the collar. Each collar has five holes.
 
Size Adjustable Length Center Hole Length
XS 12" to 15" 13.5"
S 13" to 17" 15"
M 15" to 19" 17"
L 17" to 21" 19"
XL 19" to 23" 21"
 
To find the correct size for your dog, measure your dog's neck loosely and add one inch. This is the center hole length you need. If this is not equal to the center hole length of a collar, choose the nearest center hole length, there are two holes on either side to adjust for a larger or smaller neck.
 
For example:
  1. If your dog's loose neck measurement was 13", you would add 1" and pick a collar center hole length size closest to 14". This would be 13.5" with the XS collar.
  2. If your dog's loose neck measurement was 19.5", you would add 1" and pick the collar with the center hole length closest to 20.5". This would be 21" with the XL collar.
  3. If your dog's loose neck measurement plus 1" is exactly in between two center hole lengths, then pick the smaller size. The collar will stretch slightly with wear.

If you are not sure, please call us at 877-800-8181 to speak to a customer service representative.