Herm Sprenger Original System 4-F Stirrups offer all the benefits of System 4-F technology, but in the original style. Special treads adapt to your foot, ensuring consistent contact with stirrup. Manufactured according to strict standards and using only the highest quality materials, these irons are designed to significantly reduce strain on knee and ankle joints. They pivot simultaneously in four directions to allow for greater comfort and improved performance. This increased flexibility helps alleviate tension and pain in the hips, knees and ankles by softening the impact on joints, cartilage and ligaments. Note: due to rubber covering, stirrup is 1/4" smaller than the size given.