Non-stop dogwear X Back Harness for Pulling, Sledding, Canicross, Bikejoring & Mushing Extremely versatile, the Nansen Nome X back is the number one choice of professional mushers worldwide. You will see famous Iditarod mushers, open class sprint mushers and 4 dog sprint mushers use this harness on a variety of dogs: Alaskan Huskies, Greysters, GSP's, Eurohounds and Polar Breeds. Sizing is easy but remember that these are designed more for sled dogs with a certain shape! If you are looking for an everyday harness for your household pet we recommend the Non-stop dogwear Half Harness or Freemotion Harness. Mushers who train in Alaska, Norway, Canada, Scandinavia love the superior 3M reflective striping which lights up the team at night and keeps your dogs safe. Features an "anti-crabbing" metal ring at the base of the harness which keeps the harness centered on your dog's chest and prevents rub. The rear piece is unique in the way that it automatically balances the pull point for dogs who work diagonally. For the perfect fit (and it should not be too loose): Measure your dog's neck. Smaller sled dogs are size 4 and 5. Medium sled dogs are 6 and 7. Larger and longer sled dogs are size 8 and 9. Dogs with thicker necks need a half size. 4.5 and 5.5 for smaller dogs with thick necks. 6.5 and 7.5 for medium dogs with thick necks. 8.5 and 9.5 for larger and longer dogs with thick necks.See the measurements below