First off, I really like the fabric of these shirts. They have just the right amount of stretch while still feeling like a cotton shirt. I bought them to be an undershirt and that is where I went wrong. I am 5'11" and 175lbs and went for a medium, my regular size.
When I first tried them on, they felt like they would work for my purpose. But after washing them they shrunk just slightly, just enough to feel a little short for an undershirt. I wash them on "cold" setting with "very low" dryer heat setting. I do not think that is the issue, I probably should have just returned them when I noticed they were right on the edge. Unfortunately, I bought the 3-pack, so yeah.
They are a great fabric, but size accordingly and know they might shrink just a bit. Hope this helps.