The medium size adjustable harness fits my one-year old Samoyed perfectly. I may not have even needed to get the adjustable one. He loves to pull when wearing it, either me on snowshoes or skis (with the belt made to match it) or a small log to which I attached an eye-bolt. The red color against the white fur stands out very well!
great quality/durability. Fits my husky like a glove!
Perfect Fit Harness
So I originally went by weight, and realized it's best to physically measure them. I decided to keep the large that are too big for the possibility of having a larger dog. But the medium harnesses they ever so graciously expedited to me are incredible! I've had some bad luck with other harnesses, so I'm constantly vigilant over multiple things, and so far I'm very impressed. And my boys look so very handsome in their new gear. I also came back for a few other items, I'm still getting used to the distance, but we love our new gear. :)
There were some things that do not fit quite nicely across my dog's back, but that could easily be because he has abnormal proportions. Other than that, it is a very good harness.