The Sidi Hyper Extension Block System is a vital replacement part for Crossfire 3 SRS boots, designed to prevent hyperextension of the ankle, instep, and posterior tendon during intense rides. Featuring a two-piece construction, this system enhances protection without compromising flexibility. Easy to install, it ensures your boots maintain their advanced protective features, helping to prevent injuries during off-road and motocross adventures. Sidi Hyper Extension Block System