The team at Proof created a performance tee that can be worn for 72 hours straight without showing any signs of wear—or, you know, odor. The 72-Hour Tee is built from the softest and strongest merino wool on the planet. To back up that claim, we’ve packed it as our only shirt on demanding excursions around the world—from Iceland and the Swiss Alps, to Mexico City and even our own backyards. Turns out, this temperature-regulating tee isn’t just for travel, it’s also our all-time bestselling tee for everyday wear.