Country Brook Design Green Paisley Step-in Dog Harness - Medium Harness fits (18in - 30in neck/ 18in - 30in girth). There are no standard sizes for dog harness. Please be sure to measure your dog's neck and chest (girth) for correct size. Measure around your dog's neck (with string or tape measure) and chest snugly where you want the harness to lay. If you have any questions or problems with sizes please give us a call before ordering. If you have any questions or problems with sizes please give us a call before ordering. 256-974-0700 Breed Recommendation: Greyhound, French Bulldog, or Collie Made in U.S.A. with top quality hardware Adjustable to fit your dog