Reviewing thermoses should be easy. Does it keep your beverage hot or cold? One point. Does it spill? Zero points. Does it fit easily in your pack? Another point. But when you spend a few months with a variety of thermoses, as the BACKPACKER staff did from mid-February through mid-May, the X factors grow exponentially. One thermos has a bullet-proof exterior but the pouring lid is now two parts instead of one. One thermos won the seal test…until the seal ended up in a dog’s mouth. And several of the testing models vanished into thin air. But there were still a few clear winners—and those winners managed trail, car, and desk with ease.