This shirt runs VERY large.  I always wear a 3XLT shirt so that's what I ordered.  I opened the package, washed it and then put it on.  The thing swallowed me up big time, it is huge.  I would estimate it is probably more of a 4XLT or 5XLT shirt.  So I ordered another one that was a 2XL and it arrived yesterday.  Surprisingly it was still big on me but tolerable enough that I'll keep it.  I could probably wear an XL version of this shirt and I haven't worn that size in 15+ years.  The shirts do appear to be of good quality and not super thin.  I suspect it will last a while.  I haven't tried returning the first one since I opened and washed it before trying it on.  But I assumed it would fit and I always wash clothes before wearing them to help get some of the dyes and chemicals out before wearing them.