Our quilted 0° Arctic Parka Liner, constructed with our patented VÆTREX™ insulating technology, is designed to wear with our Arctic Parka Shell. Combined they will keep you warm in temperatures ranging from 40º to 0°F. In an extensive double-blind test performed by the UNIVERSITY OF NORTH DAKOTA, Northern Outfitters VÆTREX™ liners were proven superior to any other garments available for extreme cold weather temperatures. The results of the test concluded: "OUNCE FOR OUNCE, VÆTREX™ IS THE MOST EFFICIENT INSULATING MATERIAL AVAILABLE TODAY." VÆTREX™ is the ideal product for any winter activity.