"What Our Gearhead® Experts Are Saying: ""This is my favorite hot-weather running shirt. It’s insanely light, super breathable, and dries fast—even when I’m dripping sweat. It doesn’t get clingy or stink either, thanks to the merino blend. Total win for trail runs and travel.""Whether we're crushing miles on the trail or chasing sunsets on the road, the Smartwool Merino Sport Ultralite Short-Sleeve Shirt is built to keep us comfortable through it all. It combines the natural performance of merino wool with the durability and quick-dry power of recycled polyester—giving us next-to-skin softness and breathable performance in one ultralight package. The athletic cut moves with us through every stride, stretch, and summit push, while the low-profile seams reduce chafing during long runs and warm-weather efforts. Lightweight enough for layering, breathable enough to wear solo, and stylish enough to wear from trail to town—this shirt is a staple in our warm-weather kit."