This is an adult Medium. I forgot to list the size. I think it would be a little large for a 9-yr old, but Aeropostle runs very small in comparison to other brands. If he is big build it probably would not be too big. It measures under arm to under arm 23 inches. The sleeves are 21 1/2 inches from underarm to the end of the sleeve. From neck to tail measures about 25 inches and it is approximately 23 inches from seam to seam at the tail of the shirt.
Oh, ok ty! It would probably be a better fit for a teen.. I don't think my nephew could wear it.. Thanks for the measurements. Hope it does well for you.. Good to see you on Listia! I sometimes see Sis. Shaw when I go see my grandma in Burkesville