Great shirt. It moves well when riding. It is good quality and super lightweight. I usually wear an XS, and this XS fits perfectly, so definitely true to size. My only complaint: it just doesn't breathe as much as I would like, so keep that in mind when riding in warmer weather.
Rated 0 on a scale of minus 2 to 2, where minus 2 is Runs Small, 0 is True to Size and 2 is Runs Big