I found a closeout sale that had a few of these for a great price, and even though they didn't have my usual size, I examined closely and noticed that it has lots of stretch.  At the price, I couldn't resist going ahead and buying one even though it was two sizes smaller than my usual.  It had plenty of stretch to allow me to squeeze into it.  I enjoy tight compression shirts, especially when sleeping, and this fit the bill perfectly,  It is really tight, yet fits well, doesn't appear to be too small, doesn't feel binding at any point, and holds its original shape so it doesn't lose its compression.  It actually fit perfectly, tightly around and in the under arm area.  I was surprised to discover that the arm length of the two size smaller shirt were still long enough to cover the wrists.  I do have a UA compression shirt that is three sizes larger than this Champion C9 which fits almost the same. This one is as nice as the UA