Not that kind of hot and dirty ... The Ex Officio Men's Sol Cool Crew is for the guys who work up a sweat at the mere idea of backpacking, hiking, climbing, cycling, mountain biking, running, or any other hot-weather activity. Ex Officio made this long-sleeve crew out of polyester and spandex for a comfortable amount of stretch, and then added Ice-Fil technology (containing xylitol derived from birch trees) to wick moisture and keep you at a solid five degrees cooler than the air around you. Ice-Fil technology also gives this shirt antimicrobial properties, meaning it won't stink as badly as you do after a difficult hike under the sun. Its natural fit includes raglan sleeves and an underarm gusset to give you the mobility you need to climb comfortably. Flatlock seams add comfort when you're backpacking with a heavy load on your shoulders.