It's not tight as I expected it to be, but that is okay, I wear medium so it fits me just fine.  Leaves your arms completely uncovered, so you can go ahead and get the tan outside of the regular t-shirt line on your upper arms.  Also I have just one recommendation: that if you are getting this type of shirt for more than just tan line/arm reveal, you get the size smaller than what you normally wear so it will be tight against your body, unless the size you regularly wear is already that way.