The Muck Boot Company Men's Arctic Sport Mid Winter Boot is a winter boot designed to offer warmth and protection from the elements. These waterproof Muck boots provide comfort and warmth for the most extreme outdoor conditions. Your feet will thank you for these toasty warm Muck winter boots. You'll absolutely love these insulated Muck boots! Classic Muck style that will keep feet warm to -40 degrees Insulated Muck boots offer a 5mm CR Flex-foam and a warm fleece lining 2mm thermal foam under the removable foot bed for added warmth Waterproof Muck boots feature rugged outsole for traction Muck winter boots are 100% waterproof Stretch-fit top-line binding snugs leg to keep warmth in and cold out 5mm neoprene bootie with four-way stretch nylon