I believed all of the reviews that it runs small and ordered L. Big mistake, will have to use it as an outer layer. So I purchased a second one in M, which fits perfect. Unless you have a beer gut, order in your regular size.
Decent quality, does not develop that polyester smell if you sweat in it. Good as a layering piece for walking, or as an outer layer for running 10 degrees and below.
Sleeves are too long, and will twist during regular wear. The top pocket is useful, but prevents the garment from sitting flat on your chest, and makes folding it difficult.
Overall happy with the purchase.