Whoa, you guys.  These are the smoothest, most breathable, just soft and amazing undershirts.  I ordered a medium for my husband (he's kind of a S/M size) and the mediums were too big to lie flat under shirts.  We got Small for him (totally the right size) and I kept the mediums to sleep in.  He wants a wardrobe of these, and I can't lie, I kind of do too.  We've had one pack for three months and they are holding up very well in weekly washing.