This is our first time purchasing the Under Armour shirts and my 8 year old loves them.  She is very thin and doesn't like shirts that are baggy so the 6 fit her well, I just wish it was a tad longer since she primarily wears these with leggings.  Next time I might try the next size up and see how that goes.  These wash well and are thin enough to be good for warmer days without being so thin they are inappropriate.