The new Kid's Rugged II will protect your child's feet in severe cold with new 5mm CR Flex-Foam insulation backed with a fleece lining. This lining adds extra insulation to keep cold out for kids that want to stay outside playing in the snow all day. The Rugged II provides classic Muck comfort and warmth in an exceptionally durable and Slip Resistant package. These boots are easy to slip on/off and come in a variety of fun, bright colors. Material: Rubber.