“I've got a medium build, muscular but not slim. Medium is the right size to go. I love this store, as it gets different bodies. I will say the "heavyweight" is exactly as described! It has some heft. It probably isn't a shirt for the summer here in Texas, but it'll be perfect for most of you that live in a climate that's ummm... not tempermental. Looking forward to rocking this in cooler weather.”