The Mountain Horse(R) Rimfrost Rider III Tall Boot is the original versatile boot that started it all has been upgraded, now featuring Extensia foot part which has been tested to withstand one million flexes in 14°F weather. Heat-insulating Thermolite® lining will keep feet and legs warm while the waterproof construction keeps feet dry up to the start of the zipper. Sturdy and durable YKK® zipper for easy entry and exit. Built in steel shank for increased stability. Fabric: Duralon™/Extensia. Insulation: 200g Thermolite®