I purchased the L-XXL, mostly cuz I am normally a size Large and I didn't want to risk the S-M not fitting, as I am a bit of a chubby girl. I'm 5ft tall and weight 151lbs and this harness fit great! It's the first harness I've ever purchased and I'm glad I did! I plan to wear it over some of my tops when I get chances to go places!
Fair Warning: I did state the harness fit good, but some of the loops I had to belt down on the last loop to fit properly, so be wary of that if you are in between Medium and Large size.