For those that need a warm winter base layer but tend to overheat, the Helly Hansen Lifa Merino Midweight 1/2 Zip Base Layer Top has you covered. A 100% merino wool exterior provides warmth while and moisture-wicking Lifa interior adds breathability against sweat. And when you feel the heat start to encroach, zip down the front to cool down as much or as little as you need. Light the snow on fire, comfortably.