Stay warm and dry in the harshest conditions with 509��s Active Layering System featuring Cold Armor technology. Pairing 509��s base and mid layers with 509��s outerwear creates a high-performance layering system that works together to keep you comfortable no matter what. The system starts with our lightest base layer, the 509 FZN Base LVL 1 Pant��a close fitting next-to-skin layer designed to actively wick away heat-robbing moisture so you stay dry and comfortable all day long.