The Men's Le Chameau Vierzonord Extreme Wellies are an award winning pair of boots, providing unbeatable protection against the cold. The Vierzonord Extreme are lined throughout with 5mm of premium quality neoprene (compared to 2mm in the standard Vierzonord), to insulate up to -25 degrees. Specifically for this boot, Le Chameau have developed a removable aluminised insole which reflects body heat back into the boot further maintaining a comfortable temperature. This double protection makes it very difficult for cold to penetrate the boots from the ground. These practical features and use of technical materials make the Vierzonord Extreme ideal for the coldest of winter days or for those who really feel the cold. Maximum calf width for this boot is 43cm.