Mons just does not miss. The Olympus 1/2 is a perfect baselayer - offering unrivalled warmth to weight ratio and strategically placed mesh panels to ensure breathability. Dont worry about stretching this out, the added elastane helps keep its shape long term. The half-zip is clutch on those days when you are working really hard and need some breathability. Mech underarm panals and raglan sleeves for ideal mobility.