Harlestons Measurements
Small Medium Large XL XXL
Blazer Size 35-37 36-40 40-42 42-45 45+
Chest Size 20 21 23 25 26

 

For reference, a 5'11, 175 lb man would most likely wear a size medium. If you are in between sizes please size up for a more relaxed fit or size down for a slim fit.