Warm, versatile Polartec® Power Stretch® Pro base layer for cold conditions. The Kyanite Baselayer Bottom was previously the Rho Heavyweight Bottom.The Kyanite Baselayer is 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, and a zippered thigh pocket secures small essentials. What's been updated: Updated with a new fabric made with recycled content.