Bought this for our 65lb senior weim we adopted last month. She is tough to fit in Ruffwear harnesses b/c she is very petite, but deep chest at 31”. I bought the padded version of this harness in a medium & after a month of wearing it, she rubbed off a bunch of the hair on her chest (she has thin coat, sensitive skin, 8 years of poor nutrition, and is learning not to pull). I bought this non-padded version in large. It seems to fit well, excited to take her for a walk in it tomorrow. I will say, we have an old flag line harness & it’s lasted thru 4 senior dogs, the quality of Ruffwear products is exceptional - from collars to leashes, to coats, to bowls, to harnesses. Once you get the fit correct, you will get more than your money’s worth!