Ive been waiting for them to put out a 100% polyester shirt (most of their product line is organic cotton) and they went above and beyond with this one. Its a very technical shirt and extremely comfortable. It has a performance fit with really high arm holes so its awesome if you are wearing it with a backpack or while climbing. The side/back panels are 2 layer mesh so it breathes really really well, also great when wearing a backpack. I literally did not stop wearing it for a week when I got it, and then lived in it on Isle Royale and it was awesome!! Wicked sweat well and kept me cool, and didn't smell as bad as most poly shirts do after a week of hiking. A MUST buy!