These run waaay big. I have their Cthulu rash guard. I weigh 165 and got one in medium. I'm lean with an athletic build and I don't skip leg day, but the rash guard was way too big on me. Body fit loose like a T shirt and the upper arms were loose too. Forearms werent loose enough to wrinkle but no compression.

I guess I prefer my rash guards tight so they don't get caught while rolling... i guess I'll use it for muay thai duty? I could have exchanged but shipping back and forth from Australia seemed... meh..  

i recently got a size medium Raven rashguard but it was way too big... hesitant to buy another rashguard online because Ravens size chart saud mediums fit guys at 150lbs. I'm 5'10" 160-165 lean, but with big legs. 40" jacket size. Should i get a large?