Made of Patagonia's warmest expedition weight Capilene 4 farbric, the Men's Capilene 4 EW Zip Neck is the perfect baselayer for exceptionally cold conditions. The deep front zip makes layering much easier and also allows you to vent quickly when overheating. The fleece interior fabric is brushed for added warmth and the smooth exterior structure is durable and allows for easy layering.