The Sprenger Jointed Irons are also called "System 4 Stirrups". They are safety stirrups with 4 links offering more security and maximum comfort. The stirrup pivots in 4 directions simultaneously, relieves tension in the hips, knees, ankles and calves and softens the impact on cartilage and ligaments. The high flexibility enables the stirrup to adapt perfectly to all movements. Note: due to rubber covering, stirrup is actually ¼ smaller than size given.