Along with this Helium Paddling Jacket I have recently purchased NRS Mens Endurance Paddling Pants. Both ran small (in order to wear over a warm layer on the river). I am a very average 5'10", 180 lbs man. I first purchased "Large" in each item but had to return for XL. I haven't received the pants back in XL yet but the Helium jacket fits about right in XL. I have been running into this same problem with other apparel manufactured in Asia. It's getting old returning stuff!