The Mountain Horse Rimfrost Rider Tall Boot is a super warm and comfortable tall winter boot designed for years of hard use. Updated with an Extensia foot, the Rimfrost boot is now more durable than ever. The Extensia material has been tested to withstand one million flexes at 14 degrees Fahrenheit so you can be confident that these boots won't crack or split their first season. Extensia foot is more flexible and resistant to cracks in cold weather Duralon fabric on the calf Heat insulating Thermolite lining covered by a soft foam material will keep legs, feet and toes toasty warm Sturdy and durable YKK zipper for easy on/off Durable elastic accordion inserts along calf area for improved individual fit Full length hydro-tech material walls safeguard the zipper from excessive chafing while providing protection for your saddle Breathable, waterproof Hydrotech membrane prevents water from entering into the foot part up to the zipper Removable insole made of cozy, warm pile lining keeps your feet dry and warm on cold winter days Built in steel shank for increased stability while walking or riding