They are true to size for the sport crew ones, but the flame shirts run small. I wear XL on all of my shirts normally, and the sport crew shirt fits fine and doesn't shrink as long as you wash it in cold.
I have popped buttons off of both of my flame shirts while bowling. Too restrictive for what I would consider an XL. If I ever get another of these, I'll go for the XXL.
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~SprayNpray
-formerly known as SawFreak