I got a white tee in XL size and it turned out to be too big. However, the fabric felt heavy and better than those super thin T-shirts that everybody else offers. So I ordered one in L size but in a different color. Well, this time the tee is a little too small. Also, the fabric is nowhere as heavy as the tee I received earlier.
I suspect that Hanes has good intentions to offer a slightly better product but these are still mass produced in low wage factories. There seems to be inconsistency in quality and sizing. You may get lucky or you may not.
Lastly, I recommend sticking to whites and lighter shades as the quality of dye in darker tees seems rather poor and will fade rapidly.