Layering well and staying dry are key even in warmer weather, so Marmot designed the Men's ThermalClime Sport Crew Short-Sleeve Shirt to be a quick-drying, moisture-wicking baselayer that's suitable for all activities in mild conditions. ThermalClime technology uses a Polartec PowerDry polyester fabric that's woven with smaller threads on the inside of the fabric, significantly increasing moisture transfer while remaining slightly stretchy. The Sport Crew also features flat-locked seams for increased comfort, and a tag-free neckline to eliminate irritation. If only they could do something to stop your nips from bleeding on those long runs ...