Warm, versatile Polartec® Power Stretch® Pro base layer for cold conditions. The Kyanite Baselayer Zip Neck was previously the Rho Heavyweight Zip Neck.The Kyanite Baselayers are made for cold days and mixed output. On the move, the Polartec® Power Stretch® Pro stretches for outstanding freedom of movement. During rest phases – or when it gets really cold – the fleece’s soft brushed interior traps heat to keep you warm. The fleece’s durable nylon outer has a smooth face for comfort under layers, the tall collar extends warmth, and the deep front zipper aids heat dump and makes on-and-off easier. What's been updated: Updated with a new fabric made with recycled content.