Mons Royale's Olympus line is the warmest of their baselayer collection. At 250g this is meant to be your cold weather gear. A heavyweight merino top that is moisture wicking, naturally anti-microbial, and meant to help start off your layering the right way. An asymetrical half zip allows for ventilation as well as mesh paneled underarms. A slim fit keep the merino close to your skin so it can't work it's natural wonders.