This ultra-lightweight CloudMerino™ long-sleeve tee provides thermoregulation and moisture management in all conditions and seasons. Weighs 136 grams. Heat sensitive wire changes color when exposed to heat. It's made from CloudMerino™ Optimo wool jersey from Japan, the world's finest wool. Featuring thermoregulating properties, CloudMerino™ is silky soft, naturally odor resistant, and weighs next to nothing. CloudMerino™ is versatile and resilient in all types of weather and conditions. On hot runs, the finely knit fabric wicks sweat away from your body to keep you cool, while the wool’s folds retain your body heat in the cold. Unlike most fabrics, even when CloudMerino™ is wet, it keeps you warm. - CloudMerino™ CloudMerino™ is made in Japan from 100% Optimo Merino wool. The mill was founded in 1964 and is known for its high-quality jersey and innovative natural fabrics. The wool’s porous fibers wick sweat away from your skin so you never feel clammy on a run, and it dries quickly when wet as the wool’s folds trap your body heat. Finely knitted, CloudMerino™ is ultra-lightweight, silky soft, and naturally odor-resistant. Its thermoregulating properties and moisture management capabilities make it ideal for use throughout the seasons, providing continued comfort all year round.