Our Otter Polar-D Super System is the ultimate, warm & comfy system. This undersuit/base layer comes with many layering options from sweatshirt, cardigan style jacket, trousers & socks. The special material we use is a double layer of cloth, with the inner layer being super comfy, warm fleece. This keeps you nice & cosy & warm. The outer layer is a great looking micro-fleece, this catches any heat that is trying to escape past the inner layers. The gap between the two cloths catches most of the surplus heat and passes it back to the inner fleece, keeping you extra cosy & warm.