53% Poly, 43% supplex nylon
This is a great looking shirt, though it fits a bit large (I ordered a small, am 5'7'' and it is still a little larger than I would prefer), but not so large that it makes a huge difference. Also, the fabric is definitely very lightweight, and see this as being a great moisture-wicking shirt for when I am on my thru-hike of the AT this summer. My biggest concern is the durability of such a lightweight shirt, especially at the cost of the shirt. I will gladly write another review in the fall when I return from the trail to let you know how it held up.
Shell: 57% Polyester, 43% Supplex nylon
Liner: 57% recycled Polyester, 43% Polyester
The shell is 57% poly and 43% nylon. The lining is 57% recycled poly and 43% poly