This is a great slim rash guard. The fit is very very small, so read the reviews to see fit guides.  I bought a small for a girl who is 51 and 77 pounds. She is about a girls size 10 in her chest. We ordered the small and it is a smidge big in the chest and arms. We could have ordered the xsmall but I was afraid of it being too small. It would have fit her perfect. The shirt is nice and long and I like how the arms provide some sun protection down to almost the elbow.  Fabric is thick and nice. Shell grow into it and well have it for next year as well.