I've tested Icebreaker's Tech Lite T-Shirt over multiday climbing outings in Colorado and a multiday fishing & hiking expedition in Zambia, South Africa and Namibia. I wore the shirts as a base layer in freezing and near-freezing weather and as an outer in 30C+ weather. I intentionally wore the shirt for several days in a row without washing - no smell. The shirts look good and are also comfortable. I'm 5'11", 175-180 pounds (depending on beer consumption), 42" chest, and bought the large, which fits nicely. I highly recommend this product and have sent all of my old cotton t-shirts to Goodwill.