When I received this Merino Wool Heavyweight, I knew I had a substantial garment in the bag even before opening. It was exactly what I wanted. The 370 GSM fabric weight will definitely keep me warm in the harshest of climates. I already have 150, 210, 250 and 400 weight Merino Wool base layers, however, none with the Kryptek Highlander Camo pattern. I prefer Merino Wool base layers period. The polyester, fleece and lofted fleece base layers from other brands just don't cut it for me. I need the warm, dry, no stink properties that only Merino Wool can offer. For me, it's the perfect base layer for Colorado winters. For size comparison, I am 6'4"; 225#; 40" waist; 37" sleeve length. Size 2XL fits me perfectly in shirt and sleeve length. I am happy Kryptek has offered this heavyweight which will preclude me from wearing anything underneath except for really cold, blustery days.