I have a few Derminpro shirts. All are size medium and fit great, except this one. The medium ran small (tight), so I returned it for a large and that one fits great. The only reason for the 4 stars is the inconsistent size with their other products. Inexpensive, well made, and light weight. I live in Hawaii and use these for golf. They stay cool and wick moisture. Also look great off the course.