Previously the Rho AR Zip Neck, the Rho Heavyweight Zip Neck – Arc’teryx warmest base layer top – are made for cold days and mixed output. During rest phases – or when it gets really cold – the fleece traps heat to keep you warm.  Features: Rho series: Thermally efficient base layer with excellent moisture management properties and stretch comfort Polartec® Power Stretch® Pro combines a highly durable nylon outer with a soft brushed polyester interior: Next-to-skin moisture management - wicks moisture away from the skin to maximise dryness and warmth Thermal efficiency with a great warmth-to-weight ratio Stretchy fabric provides outstanding freedom of movement Smooth outer surface for easy layering Articulated patterning for unrestricted mobility Tall collar for added warmth Deep front zipper for easy on and off, rapid ventilation Chest pocket with zip Trim fit: keeps warmth close to the body and makes it an ideal layering piece Weight: 285 g Sustainability: contains materials that meet the bluesign® criteria Materials: Polartec® Power Stretch® Pro - 53% Polyester, 38% Nylon, 9% Elastane Arc'teryx Men's Rho Heavyweight Zip Neck