Heated Socks by HeatMax are designed with the dedicated outdoorsman in mind. The main feature of the Heated Socks by HeatMax is the elastic band that surrounds the top and bottom of the toe area. The Foot Warm-Up inserts are the only warmers recommended for use with the Heated Socks by HeatMax. Use of any other warmer may result in excessively high temperatures that could result in burns or non-effective low temperatures